The American alligator (Alligator mississippiensis), sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile native to the Southeastern United States. It is one of the two extant species in the genus Alligator, and is larger than the only other living alligator species, the Chinese alligator.

 

Adult male American alligators measure 3.4 to 4.6 m (11.2 to 15.1 ft) in length, and can weigh up to 500 kg (1,100 lb), with unverified sizes of up to 5.84 m (19.2 ft) and weights of 1,000 kg (2,200 lb) making it the second largest member of the family Alligatoridae, after the black caiman. Females are smaller, measuring 2.6 to 3 m (8.5 to 9.8 ft) in length. The American alligator inhabits subtropical and tropical freshwater wetlands, such as marshes and cypress swamps, from southern Texas to North Carolina. It is distinguished from the sympatric American crocodile by its broader snout, with overlapping jaws and darker coloration, and is less tolerant of saltwater but more tolerant of cooler climates than the American crocodile, which is found only in tropical and warm subtropical climates.

 

American alligators are apex predators and consume fish, amphibians, reptiles, birds, and mammals. Hatchlings feed mostly on invertebrates. They play an important role as ecosystem engineers in wetland ecosystems through the creation of alligator holes, which provide both wet and dry habitats for other organisms. Throughout the year (in particular during the breeding season), American alligators bellow to declare territory, and locate suitable mates. Male American alligators use infrasound to attract females. Eggs are laid in a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water. Young are born with yellow bands around their bodies and are protected by their mother for up to one year.[

 

The conservation status of the American alligator is listed as Least Concern by the International Union for Conservation of Nature. Historically, hunting had decimated their population, and the American alligator was listed as an endangered species by the Endangered Species Act of 1973. Subsequent conservation efforts have allowed their numbers to increase and the species was removed from endangered status in 1987. The species is the official state reptile of three states: Florida, Louisiana, and Mississippi.

 

Taxonomy

 

The American alligator was first classified by French zoologist François Marie Daudin as Crocodilus mississipiensis in 1801. In 1807, Georges Cuvier created the genus Alligator; the American alligator and the Chinese alligator are the only extant species in the genus. They are grouped in the family Alligatoridae with the caimans. The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator than to either the Nile crocodile (Crocodylus niloticus) or the gharial (Gavialis gangeticus).

 

Phylogeny

Members of this superfamily first arose in the late Cretaceous, about 100–65 million years ago (Mya). Leidyosuchus of Alberta is the earliest known fossil, from the Campanian era 83 to 72 Mya. Fossil alligatoroids have been found throughout Eurasia, because bridges across both the North Atlantic and the Bering Strait connected North America to Eurasia about 66 to 23 Mya.

 

Alligators and caimans split in North America during the late Cretaceous, and the caimans reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period, from about 23 to 2.58 Mya. The Chinese alligator likely descended from a lineage that crossed the Bering land bridge during the Neogene. Fossils identical to the existing American alligator are found throughout the Pleistocene, from 2.5 million to 11.7 thousand years ago. In 2016, a Miocene (about 23 to 5.3 Mya) fossil skull of an alligator was found at Marion County, Florida. Unlike the other extinct alligator species of the same genus, the fossil skull was virtually indistinguishable from that of the modern American alligator. This alligator and the American alligator are now considered to be sister taxa, meaning that the A. mississippiensis lineage has existed in North America for over 8 million years.

 

The alligator's full mitochondrial genome was sequenced in the 1990s, and it suggests the animal evolved at a rate similar to mammals and greater than birds and most cold-blooded vertebrates. However, the full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.

 

Characteristics

 

American alligator skull

Domestic American alligators range from long and slender to short and robust, possibly in response to variations in factors such as growth rate, diet, and climate.

 

Size

The American alligator is a relatively large species of crocodilian. On average, it is the largest species in the family Alligatoridae, with only the black caiman being possibly larger. Weight varies considerably depending on length, age, health, season, and available food sources. Similar to many other reptiles that range expansively into temperate zones, American alligators from the northern end of their range, such as southern Arkansas, Alabama, and northern North Carolina, tend to reach smaller sizes. Large adult American alligators tend to be relatively robust and bulky compared to other similar-length crocodilians; for example, captive males measuring 3 to 4 m (9 ft 10 in to 13 ft 1 in) were found to weigh 200 to 350 kg (440 to 770 lb), although captive specimens may outweigh wild specimens due to lack of hunting behavior and other stressors.

 

Large male American alligators reach an expected maximum size up to 4.6 m (15 ft 1 in) in length and weighing up to 500 kg (1,100 lb), while females reach an expected maximum of 3 m (9 ft 10 in). However, the largest free-ranging female had a total length of 3.22 m (10 ft 7 in) and weighed 170 kg (370 lb). On rare occasions, a large, old male may grow to an even greater length.

 

Largest

During the 19th and 20th centuries, larger males reaching 5 to 6 m (16 ft 5 in to 19 ft 8 in) were reported. The largest reported individual size was a male killed in 1890 on Marsh Island, Louisiana, and reportedly measured at 5.84 m (19 ft 2 in) in length, but no voucher specimen was available, since the American alligator was left on a muddy bank after having been measured due to having been too massive to relocate. If the size of this animal was correct, it would have weighed about 1,000 kg (2,200 lb). In Arkansas, a man killed an American alligator that was 4.04 m (13 ft 3 in) and 626 kg (1,380 lb). The largest American alligator ever killed in Florida was 5.31 m (17 ft 5 in), as reported by the Everglades National Park, although this record is unverified. The largest American alligator scientifically verified in Florida for the period from 1977 to 1993 was reportedly 4.23 m (13 ft 11 in) and weighed 473 kg (1,043 lb), although another specimen (size estimated from skull) may have measured 4.54 m (14 ft 11 in). A specimen that was 4.5 m (14 ft 9 in) long and weighed 458.8 kg (1,011.5 lb) is the largest American alligator killed in Alabama and has been declared the SCI world record in 2014.

 

Average

American alligators do not normally reach such extreme sizes. In mature males, most specimens grow up to about 3.4 m (11 ft 2 in) in length, and weigh up to 360 kg (790 lb), while in females, the mature size is normally around 2.6 m (8 ft 6 in), with a body weight up to 91 kg (201 lb). In Newnans Lake, Florida, adult males averaged 73.2 kg (161 lb) in weight and 2.47 m (8 ft 1 in) in length, while adult females averaged 55.1 kg (121 lb) and measured 2.22 m (7 ft 3 in). In Lake Griffin State Park, Florida, adults weighed on average 57.9 kg (128 lb). Weight at sexual maturity per one study was stated as averaging 30 kg (66 lb) while adult weight was claimed as 160 kg (350 lb).

 

Relation to age

There is a common belief stated throughout reptilian literature that crocodilians, including the American alligator, exhibit indeterminate growth, meaning the animal continues to grow for the duration of its life. However, these claims are largely based on assumptions and observations of juvenile and young adult crocodilians, and recent studies are beginning to contradict this claim. For example, one long-term mark-recapture study (1979–2015) done at the Tom Yawkey Wildlife Center in South Carolina found evidence to support patterns of determinate growth, with growth ceasing upon reaching a certain age (43 years for males and 31 years for females).

 

Sexual dimorphism

While noticeable in very mature specimens, the sexual dimorphism in size of the American alligator is relatively modest among crocodilians. For contrast, the sexual dimorphism of saltwater crocodiles is much more extreme, with mature males nearly twice as long as and at least four times as heavy as female saltwater crocodiles. Given that female American alligators have relatively higher survival rates at an early age and a large percentage of given populations consists of immature or young breeding American alligators, relatively few large mature males of the expected mature length of 3.4 m (11 ft 2 in) or more are typically seen.

 

Color

Dorsally, adult American alligators may be olive, brown, gray, or black. However, they are on average one of the most darkly colored modern crocodilians (although other alligatorid family members are also fairly dark), and can be reliably be distinguished by color via their more blackish dorsal scales against crocodiles. Meanwhile, their undersides are cream-colored. Some American alligators are missing or have an inhibited gene for melanin, which makes them albino. These American alligators are extremely rare and almost impossible to find in the wild. They could only survive in captivity, as they are very vulnerable to the sun and predators.

 

Jaws, teeth, and snout

 

American alligators have 74–80 teeth. As they grow and develop, the morphology of their teeth and jaws change significantly. Juveniles have small, needle-like teeth that become much more robust and narrow snouts that become broader as the individuals develop. These morphological changes correspond to shifts in the American alligators' diets, from smaller prey items such as fish and insects to larger prey items such as turtles, birds, and other large vertebrates. American alligators have broad snouts, especially in captive individuals. When the jaws are closed, the edges of the upper jaws cover the lower teeth, which fit into the jaws' hollows. Like the spectacled caiman, this species has a bony nasal ridge, though it is less prominent. American alligators are often mistaken for a similar animal: the American crocodile. An easy characteristic to distinguish the two is the fourth tooth. Whenever an American alligator's mouth is closed, the fourth tooth is no longer visible. It is enclosed in a pocket in the upper jaw.

 

Bite

Adult American alligators held the record as having the strongest laboratory-measured bite of any living animal, measured at up to 13,172 N (1,343.2 kgf; 2,961 lbf). This experiment had not been, at the time of the paper published, replicated in any other crocodilians, and the same laboratory was able to measure a greater bite force of 16,414 N (1,673.8 kgf; 3,690 lbf) in saltwater crocodiles; notwithstanding this very high biting force, the muscles opening the American alligator's jaw are quite weak, and the jaws can be held closed by hand or tape when an American alligator is captured. No significant difference is noted between the bite forces of male and female American alligators of equal size. Another study noted that as the American alligator increases in size, the force of its bite also increases.

 

Movement

 

When on land, an American alligator moves either by sprawling or walking, the latter involving the reptile lifting its belly off the ground. The sprawling of American alligators and other crocodylians is not similar to that of salamanders and lizards, being similar to walking. Therefore, the two forms of land locomotion can be termed the "low walk" and the "high walk". Unlike most other land vertebrates, American alligators increase their speed through the distal rather than proximal ends of their limbs. In the water, American alligators swim like fish, moving their pelvic regions and tails from side to side. During respiration, air flow is unidirectional, looping through the lungs during inhalation and exhalation; the American alligator's abdominal muscles can alter the position of the lungs within the torso, thus shifting the center of buoyancy, which allows the American alligator to dive, rise, and roll within the water.

 

Distribution

 

American alligators, being native both to the Nearctic and Neotropical realms, are found in the wild in the Southeastern United States, from the Lowcountry in South Carolina, south to Everglades National Park in Florida, and west to the southeastern region of Texas. They are found in parts of North Carolina, South Carolina, Georgia, Florida, Louisiana, Alabama, Mississippi, Arkansas, Oklahoma and Texas. Some of these locations appear to be relatively recent introductions, with often small but reproductive populations. Louisiana has the largest American alligator population of any U.S. state. In the future, possible American alligator populations may be found in areas of Mexico adjacent to the Texas border. American alligators have been naturally expanding their range into Tennessee, and have established a small population in the southwestern part of that state via inland waterways, according to the state's wildlife agency. They have been extirpated from Virginia, and occasional vagrants from North Carolina wander into the Great Dismal Swamp.

 

Conservation status

 

American alligators are currently listed as least concern by the IUCN Red List, even though from the 1800s to the mid-1900s, they were being hunted and poached by humans unsustainably.

 

Historically, hunting and habitat loss have severely affected American alligator populations throughout their range, and whether the species would survive was in doubt. In 1967, the American alligator was listed as an endangered species (under a law that was the precursor Endangered Species Act of 1973), since it was believed to be in danger of extinction throughout all or a significant portion of its range.

 

Both the United States Fish and Wildlife Service (USFWS) and state wildlife agencies in the South contributed to the American alligator's recovery. Protection under the Endangered Species Act allowed the species to recuperate in many areas where it had been depleted. States began monitoring their American alligator populations to ensure that they would continue to grow. In 1987, the USFWS removed the animal from the endangered species list, as it was considered to be fully recovered. The USFWS still regulates the legal trade in American alligators and their products to protect still endangered crocodilians that may be passed off as American alligators during trafficking.

 

American alligators are listed under Appendix II of the Convention on International Trade in Endangered Species (CITES) meaning that international trade in the species (including parts and derivatives) is regulated.

 

Habitat

They inhabit swamps, streams, rivers, ponds, and lakes. A lone American alligator was spotted for over 10 years living in a river north of Atlanta, Georgia. Females and juveniles are also found in Carolina Bays and other seasonal wetlands. While they prefer fresh water, American alligators may sometimes wander into brackish water, but are less tolerant of salt water than American crocodiles, as the salt glands on their tongues do not function. One study of American alligators in north-central Florida found the males preferred open lake water during the spring, while females used both swampy and open-water areas. During summer, males still preferred open water, while females remained in the swamps to construct their nests and lay their eggs. Both sexes may den underneath banks or clumps of trees during the winter.

 

In some areas of their range, American alligators are an unusual example of urban wildlife; golf courses are often favored by the species due to an abundance of water and a frequent supply of prey animals such as fish and birds.

 

Cold tolerance

American alligators are less vulnerable to cold than American crocodiles. Unlike an American crocodile, which would immediately succumb to the cold and drown in water at 45 °F (7 °C) or less, an American alligator can survive in such temperatures for some time without displaying any signs of discomfort. This adaptiveness is thought to be why American alligators are widespread further north than the American crocodile. In fact, the American alligator is found farther from the equator and is more equipped to handle cooler conditions than any other crocodilian. When the water begins to freeze, American alligators go into a period of brumation; they stick their snouts through the surface, which allows them to breathe above the ice, and they can remain in this state for several days.

 

Ecology and behavior

Basking

 

American alligators primarily bask on shore, but also climb into and perch on tree limbs to bask if no shoreline is available. This is not often seen, since if disturbed, they quickly retreat back into the water by jumping from their perch.

 

Holes

American alligators modify wetland habitats, most dramatically in flat areas such as the Everglades, by constructing small ponds known as alligator holes. This behavior has qualified the American alligator to be considered a keystone species. Alligator holes retain water during the dry season and provide a refuge for aquatic organisms, which survive the dry season by seeking refuge in alligator holes, so are a source of future populations. The construction of nests along the periphery of alligator holes, as well as a buildup of soils during the excavation process, provides drier areas for other reptiles to nest and a place for plants that are intolerant of inundation to colonize. Alligator holes are an oasis during the Everglades dry season, so are consequently important foraging sites for other organisms. In the limestone depressions of cypress swamps, alligator holes tend to be large and deep, while those in marl prairies and rocky glades are usually small and shallow, and those in peat depressions of ridge and slough wetlands are more variable.

 

Bite and mastication

The teeth of the American alligator are designed to grip prey, but cannot rip or chew flesh like teeth of some other predators (such as canids and felids), and depend on their gizzard, instead, to masticate their food. The American alligator is capable of biting through a turtle's shell or a moderately sized mammal bone.

 

Tool use

American alligators have been documented using lures to hunt prey such as birds. This means they are among the first reptiles recorded to use tools. By balancing sticks and branches on their heads, American alligators are able to lure birds looking for suitable nesting material to kill and consume. This strategy, which is shared by the mugger crocodile, is particularly effective during the nesting season, in which birds are more likely to gather appropriate nesting materials. This strategy has been documented in two Florida zoos occurring multiple times a day in peak nesting season and in some parks in Louisiana. The use of tools was documented primarily during the peak rookery season when birds were primarily looking for sticks.

 

Aquatic vs terrestrial

 

Fish and other aquatic prey taken in the water or at the water's edge form the major part of American alligator's diet and may be eaten at any time of the day or night. Adult American alligators also spend considerable time hunting on land, up to 160 feet (50 m) from water, ambushing terrestrial animals on trailsides and road shoulders. Usually, terrestrial hunting occurs on nights with warm temperatures. When hunting terrestrial prey, American alligators may also ambush them from the edge of the water by grabbing them and pulling the prey into the water, the preferred method of predation of larger crocodiles.

  

An American alligator in the process of consuming a box turtle

Additionally, American alligators have recently been filmed and documented killing and eating sharks and rays; four incidents documented indicated that bonnetheads, lemon sharks, Atlantic stingrays, and nurse sharks are components of the animal's diet. Sharks are also known to prey on American alligators, in turn, indicating that encounters between the two predators are common.

 

Common

American alligators are considered an apex predator throughout their range. They are opportunists and their diet is determined largely by both their size and age and the size and availability of prey. Most American alligators eat a wide variety of animals, including invertebrates, fish, birds, turtles, snakes, amphibians, and mammals. Hatchlings mostly feed on invertebrates such as insects, insect larvae, snails, spiders, and worms, as well as small fish and frogs. As they grow, American alligators gradually expand to larger prey. Once an American alligator reaches full size and power in adulthood, any animal living in the water or coming to the water to drink is potential prey. Most animals captured by American alligators are considerably smaller than itself. A few examples of animals consumed are largemouth bass, spotted gar, freshwater pearl mussels, American green tree frogs, yellow mud turtles, cottonmouths, common moorhens, and feral wild boars. Stomach contents show, among native mammals, muskrats and raccoons are some of the most commonly eaten species. In Louisiana, where introduced nutria are common, they are perhaps the most regular prey for adult American alligators, although only larger adults commonly eat this species. It has also been reported that large American alligators prey on medium-sized American alligators, which had preyed on hatchlings and smaller juveniles.

 

If an American alligator's primary food resource is not available, it will sometimes feed on carrion and non-prey items such as rocks and artificial objects, like bottle caps. These items help the American alligator in the process of digestion by crushing up the meat and bones of animals, especially animals with shells.

 

Large animals

Other animals may occasionally be eaten, even large deer or feral wild boars, but these are not normally part of the diet. American alligators occasionally prey on large mammals, such as deer, but usually do so when fish and smaller prey levels go down. Rarely, American alligators have been observed killing and eating bobcats, but such events are not common and have little effect on bobcat populations. Although American alligators have been listed as predators of the Nilgai and the West Indian manatees, very little evidence exists of such predation. In the 2000s, when invasive Burmese pythons first occupied the Everglades, American alligators have been recorded preying on sizable snakes, possibly controlling populations and preventing the invasive species from spreading northwards. However, the python is also known to occasionally prey on alligators, a form of both competition and predation. American alligator predation on Florida panthers is rare, but has been documented. Such incidents usually involve a panther trying to cross a waterway or coming down to a swamp or river to get a drink. American alligator predation on American black bears has also been recorded.

 

Domestic animals

Occasionally, domestic animals, including dogs, cats, and calves, are taken as available, but are secondary to wild and feral prey. Other prey, including snakes, lizards, and various invertebrates, are eaten occasionally by adults.

 

Birds

Water birds, such as herons, egrets, storks, waterfowl and large dabbling rails such as gallinules or coots, are taken when possible. Occasionally, unwary adult birds are grabbed and eaten by American alligators, but most predation on bird species occurs with unsteady fledgling birds in late summer, as fledgling birds attempt to make their first flights near the water's edge.

 

Fruit

In 2013, American alligators and other crocodilians were reported to also eat fruit. Such behavior has been witnessed, as well as documented from stomach contents, with the American alligators eating such fruit as wild grapes, elderberries, and citrus fruits directly from the trees. Thirty-four families and 46 genera of plants were represented among seeds and fruits found in the stomach contents of alligators. The discovery of this unexpected part of the American alligator diet further reveals that they may be responsible for spreading seeds from the fruit they consume across their habitat.

 

Cooperative hunting

Additionally, American alligators engage in what seems to be cooperative hunting. One observation of cooperative hunting techniques was where there are pushing American alligators and catching American alligators and they were observed taking turns in each position. Another observation said that about 60 American alligators gathered in an area and would form a semicircle with about half of them and would push the fish closer to the bank. Once one of the American alligators caught a fish another one would enter into its spot, and it would take the fish to the resting area. This was reported to have occurred two days in a row.

 

In Florida and East Texas

The diet of adult American alligators from central Florida lakes is dominated by fish, but the species is highly opportunistically based upon local availability. In Lake Griffin, fish made up 54% of the diet by weight, with catfish being most commonly consumed, while in Lake Apopka, fish made up 90% of the food and mostly shad were taken; in Lake Woodruff, the diet was 84% fish and largely consists of bass and sunfish. Unusually in these regions, reptiles and amphibians were the most important nonpiscivore prey, mostly turtles and water snakes. In southern Louisiana, crustaceans (largely crawfish and crabs) were found to be present in the southeastern American alligators, but largely absent in southwestern American alligators, which consumed a relatively high proportion of reptiles, although fish were the most recorded prey for adults, and adult males consumed a large portion of mammals.

 

In East Texas, diets were diverse and adult American alligators took mammals, reptiles, amphibians, and invertebrates (e.g. snails) in often equal measure as they did fish.

 

Vocalizations

 

Mechanism

An American alligator is able to abduct and adduct the vocal folds of its larynx, but not to elongate or shorten them; yet in spite of this, it can modulate fundamental frequency very well. Their vocal folds consists of epithelium, lamina propria and muscle. Sounds ranged from 50 to 1200 Hz. In one experiment conducted on the larynx, the fundamental frequency depended on both the glottal gap and stiffness of the larynx tissues. As the frequency increases, there's high tension and large strains. The fundamental frequency has been influenced by the glottal gap size and subglottal pressure and when the phonation threshold pressure has been exceeded, there will be vocal fold vibration.

 

Calls

Crocodilians are the most vocal of all non-avian reptiles and have a variety of different calls depending on the age, size, and sex of the animal. The American alligator can perform specific vocalizations to declare territory, signal distress, threaten competitors, and locate suitable mates. Juveniles can perform a high-pitched hatchling call (a "yelping" trait common to many crocodilian species' hatchling young)[118] to alert their mothers when they are ready to emerge from the nest. Juveniles also make a distress call to alert their mothers if they are being threatened. Adult American alligators can growl, hiss, or cough to threaten others and declare territory.

 

Bellowing

Both males and females bellow loudly by sucking air into their lungs and blowing it out in intermittent, deep-toned roars to attract mates and declare territory. Males are known to use infrasound during mating bellows. Bellowing is performed in a "head oblique, tail arched" posture. Infrasonic waves from a bellowing male can cause the surface of the water directly over and to either side of his back to literally "sprinkle", in what is commonly called the "water dance". Large bellowing "choruses" of American alligators during the breeding season are commonly initiated by females and perpetuated by males. Observers of large bellowing choruses have noted they are often felt more than they are heard due to the intense infrasound emitted by males. American alligators bellow in B flat (specifically "B♭1", defined as an audio frequency of 58.27 Hz), and bellowing choruses can be induced by tuba players, sonic booms, and large aircraft.

 

Lifespan

American alligators typically live to the age of 50, and possibly over 70 years old. Males reach sexual maturity at around 11.6 years, and females at around 15.8 years. Although it was originally thought that American alligators never stop growing, studies have now found that males stop growing at around the age of 43 years, and females stop growing at around the age of 31 years.

 

Reproduction

 

Breeding season

The breeding season begins in the spring. On spring nights, American alligators gather in large numbers for group courtship, in the aforementioned "water dances". The female builds a nest of vegetation, sticks, leaves, and mud in a sheltered spot in or near the water.

 

Eggs

After the female lays her 20 to 50 white eggs, about the size of a goose egg, she covers them with more vegetation, which heats as it decays, helping to keep the eggs warm. This differs from Nile crocodiles, which lay their eggs in pits. The temperature at which American alligator eggs develop determines their sex (see temperature-dependent sex determination). Studies have found that eggs hatched at a temperature below 88.7 °F or a temperature above 94.1 °F will produce female offspring, while those at a temperature between 90.5 °F to 92.3 °F will produce male offspring. The nests built on levees are warmer, thus produce males, while the cooler nests of wet marsh produce females. The female remains near the nest throughout the 65-day incubation period, protecting it from intruders. When the young begin to hatch — their "yelping" calls can sometimes even be heard just before hatching commences — the mother quickly digs them out and carries them to the water in her mouth, as some other crocodilian species are known to do.

 

Young

The young are tiny replicas of adults, with a series of yellow bands around their bodies that serve as camouflage. Hatchlings gather into pods and are guarded by their mother and keep in contact with her through their "yelping" vocalizations. Young American alligators eat small fish, frogs, crayfish, and insects. They are preyed on by large fish, birds, raccoons, Florida panthers, and adult American alligators. Mother American alligators eventually become more aggressive towards their young, which encourages them to disperse. Young American alligators grow 3–8 in (7.6–20.3 cm) a year and reach adulthood at 6 ft (1.8 m).

 

Parasites

American alligators are commonly infected with parasites. In a 2016 Texas study, 100% of the specimens collected were infected with parasites, and by at least 20 different species of parasites, including lung pentastomids, gastric nematodes, intestinal helminths. When compared to American alligators from different states there was no significant difference in prevalence.

 

Nutria were introduced into coastal marshes from South America in the mid-20th century, and their population has since exploded into the millions. They cause serious damage to coastal marshes and may dig burrows in levees. Hence, Louisiana has had a bounty to try to reduce nutria numbers. Large American alligators feed heavily on nutria, so American alligators may not only control nutria populations in Louisiana, but also prevent them spreading east into the Everglades. Since hunting and trapping preferentially take the large American alligators that are the most important in eating nutria, some changes in harvesting may be needed to capitalize on their ability to control nutria.

 

Recently, a population of Burmese pythons became established in Everglades National Park. Substantial American alligator populations in the Everglades might be a contributing factor, as a competitor, in keeping the python populations low, preventing the spread of the species north. While events of predation by Burmese pythons on any sizable American alligators have been observed, no evidence of a net negative effect has been seen on overall American alligator populations.

 

American alligators play an important role in the restoration of the Everglades as biological indicators of restoration success. American alligators are highly sensitive to changes in the hydrology, salinity, and productivity of their ecosystems; all are factors that are expected to change with Everglades restoration. American alligators also may control the long-term vegetation dynamics in wetlands by reducing the population of small mammals, particularly nutria, which may otherwise overgraze marsh vegetation. In this way, the vital ecological service they provide may be important in reducing rates of coastal wetland losses in Louisiana. They may provide a protection service for water birds nesting on islands in freshwater wetlands. American alligators prevent predatory mammals from reaching island-based rookeries and in return eat spilled food and birds that fall from their nests. Wading birds appear to be attracted to areas with American alligators and have been known to nest at heavily trafficked tourist attractions with large numbers of American alligators, such as the St. Augustine Alligator Farm in St. Augustine, Florida.

 

Relationship with humans

Attacks on humans

 

Main article: List of fatal alligator attacks in the United States

American alligators are capable of killing humans, but fatal attacks are rare. Mistaken identity leading to an attack is always possible, especially in or near cloudy waters. American alligators are often less aggressive towards humans than larger crocodile species, a few of which (mainly the Nile and saltwater crocodiles) may prey on humans with some regularity. Alligator bites are serious injuries, due to the reptile's sheer bite force and risk of infection. Even with medical treatment, an American alligator bite may still result in a fatal infection.

 

As human populations increase, and as they build houses in low-lying areas, or fish or hunt near water, incidents are inevitable where humans intrude on American alligators and their habitats. Since 1948, 257 documented attacks on humans in Florida (about five incidents per year) have been reported, of which an estimated 23 resulted in death. Only nine fatal attacks occurred in the United States throughout the 1970s–1990s, but American alligators killed 12 people between 2001 and 2007. An additional report of alligator attacks showed a total of 376 injuries and 15 deaths recorded all from 1948 to 2004, leading this to an increase of the alligator population. In May 2006, American alligators killed three Floridians in less than a week. At least 28 fatal attacks by American alligators have occurred in the United States since 1970.

 

Wrestling

Main article: Alligator wrestling

 

Since the late 1880s, alligator wrestling has been a source of entertainment for some. Created by the Miccosukee and Seminole tribes prior to the arrival of Europeans, this tourism tradition remains popular despite criticism from animal-rights activists.

 

Farming

Main article: Alligator farm

 

Today, alligator farming is a large, growing industry in Georgia, Florida, Texas, and Louisiana. These states produce a combined annual total of some 45,000 alligator hides. Alligator hides bring good prices and hides in the 6- to 7-ft range have sold for $300 each. The market for alligator meat is growing, and about 300,000 pounds (140,000 kg) of meat are produced annually. According to the Florida Department of Agriculture and Consumer Services, raw alligator meat contains roughly 200 Calories (840 kJ) per 3-oz (85-g) portion, of which 27 Calories (130 kJ) come from fat.

 

The American alligator is the official state reptile of Florida, Louisiana, and Mississippi. Several organizations and products from Florida have been named after the animal.

 

"Gators" has been the nickname of the University of Florida's sports teams since 1911. In 1908, a printer made a spur-of-the-moment decision to print an alligator emblem on a shipment of the school's football pennants. The mascot stuck, and was made official in 1911, perhaps because the team captain's nickname was Gator. Allegheny College and San Francisco State University both have Gators as their mascots, as well.

 

The Gator Bowl is a college football game held in Jacksonville annually since 1946, with Gator Bowl Stadium hosting the event until the 1993 edition. The Gatornationals is a NHRA drag race held at the Gainesville Raceway in Gainesville since 1970.

The red-tailed hawk (Buteo jamaicensis) is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members within the genus of Buteo in North America or worldwide. The red-tailed hawk is one of three species colloquially known in the United States as the "chickenhawk", though it rarely preys on standard-sized chickens. The bird is sometimes also referred to as the red-tail for short, when the meaning is clear in context. Red-tailed hawks can acclimate to all the biomes within their range, occurring on the edges of non-ideal habitats such as dense forests and sandy deserts. The red-tailed hawk occupies a wide range of habitats and altitudes, including deserts, grasslands (from small meadows to the treed fringes of more extensive prairies), coniferous and deciduous forests, agricultural fields, and urban areas. Its latitudinal limits fall around the tree line in the subarctic and it is absent from the high Arctic. Generally it favors varied habitats with open woodland, woodland edge and open terrain. It is legally protected in Canada, Mexico, and the United States by the Migratory Bird Treaty Act.

 

The 14 recognized subspecies vary in appearance and range, varying most often in color, and in the west of North America, red-tails are particularly often strongly polymorphic, with individuals ranging from almost white to nearly all black. The subspecies Harlan's hawk (B. j. harlani) is sometimes considered a separate species (B. harlani). The red-tailed hawk is one of the largest members of the genus Buteo, typically weighing from 690 to 1,600 g (1.5 to 3.5 lb) and measuring 45–65 cm (18–26 in) in length, with a wingspan from 110–141 cm (3 ft 7 in – 4 ft 8 in). This species displays sexual dimorphism in size, with females averaging about 25% heavier than males.

 

The diet of red-tailed hawks is highly variable and reflects their status as opportunistic generalists, but in North America, they are most often predators of small mammals such as rodents of an immense diversity of families and species. Prey that is terrestrial and at least partially diurnal is preferred, so types such as ground squirrels are preferred where they naturally occur. Over much of the range, smallish rodents such as voles alternated with larger rabbits and hares often collectively form the bulk of the diet. Large numbers of birds and reptiles can occur in the diet in several areas, and can even be the primary foods. Meanwhile, amphibians, fish and invertebrates can seem rare in the hawk's regular diet, but they are not infrequently taken by immature hawks. Red-tailed hawks may survive on islands absent of native mammals on diets variously including invertebrates such as crabs, as well as lizards or birds. Like many Buteo species, they hunt from a perch most often, but can vary their hunting techniques where prey and habitat demand it. Because they are so common and easily trained as capable hunters, in the United States they are the most commonly captured hawks for falconry. Falconers are permitted to take only passage hawks (which have left the nest, are on their own, but are less than a year old) so as to not affect the breeding population. Passage red-tailed hawks are also preferred by falconers because they have not yet developed the adult behaviors that would make them more difficult to train.

 

Taxonomy

The red-tailed hawk was formally described in 1788 by German naturalist Johann Friedrich Gmelin under the binomial name Falco jamaicensis. Gmelin based his description on the "cream-coloured buzzard" described in 1781 by John Latham in his A General Synopsis of Birds. The type locality is Jamaica. The red-tailed hawk is now placed in the genus Buteo that was erected by French naturalist Bernard Germain de Lacépède in 1799.

 

The red-tailed hawk is a member of the subfamily Buteoninae, which includes about 55 currently recognized species. Unlike many lineages of accipitrids, which seemed to have radiated out of Africa or south Asia, the Buteoninae clearly originated in the Americas based on fossil records and current species distributions (more than 75% of the extant hawks from this lineage are found in the Americas). As a subfamily, the Buteoninae seem to be rather old based on genetic materials, with monophyletic genera bearing several million years of individual evolution. Diverse in plumage appearance, habitat, prey, and nesting preferences, buteonine hawks are nonetheless typically medium- to large-sized hawks with ample wings (while some fossil forms are very large, larger than any eagle alive today). The red-tailed hawk is a member of the genus Buteo, a group of medium-sized raptors with robust bodies and broad wings. Members of this genus are known as "buzzards" in Eurasia, but "hawks" in North America. Under current classification, the genus includes about 29 species, the second-most diverse of all extant accipitrid genera behind only Accipiter. The buzzards of Eurasia and Africa are mostly part of the genus Buteo, although two other small genera within the subfamily Buteoninae occur in Africa.

 

At one time, the rufous-tailed hawk (B. ventralis), distributed in Patagonia and some other areas of southern South America, was considered part of the red-tailed hawk species. With a massive distributional gap consisting of most of South America, the rufous-tailed hawk is considered a separate species now, but the two hawks still compromise a "species pair" or superspecies, as they are clearly closely related. The rufous-tailed hawk, while comparatively little studied, is very similar to the red-tailed hawk, being about the same size and possessing the same wing structure, and having more or less parallel nesting and hunting habits. Physically, however, rufous-tailed hawk adults do not attain a bright brick-red tail as do red-tailed hawks, instead retaining a dark brownish-cinnamon tail with many blackish crossbars similar to juvenile red-tailed hawks. Another, more well-known, close relative to the red-tailed hawk is the common buzzard (B. buteo), which has been considered as its Eurasian "broad ecological counterpart" and may also be within a species complex with red-tailed hawks. The common buzzard, in turn, is also part of a species complex with other Old World buzzards, namely the mountain buzzard (B. oreophilus), the forest buzzard (B. trizonatus ), and the Madagascar buzzard (B. brachypterus). All six species, although varying notably in size and plumage characteristics, in the alleged species complex that contains the red-tailed hawk share with it the feature of the blackish patagium marking, which is missing in most other Buteo spp.

 

Subspecies

At least 14 recognized subspecies of B. jamaicensis are described, which vary in range and in coloration. Not all authors accept every subspecies, though, particularly some of the insular races of the tropics (which differ only slightly in some cases from the nearest mainland forms) and particularly Krider's hawk, by far the most controversial red-tailed hawk race, as few authors agree on its suitability as a full-fledged subspecies.

 

ImageSubspeciesDistribution

Jamaican red-tailed hawk (B. j. jamaicensis)occurs throughout the West Indies (including Jamaica, Hispaniola, Puerto Rico and the Lesser Antilles) except for the Bahamas and Cuba.

Alaska red-tailed hawk (B. j. alascensis)breeds (probably resident) from southeastern coastal Alaska to Haida Gwaii and Vancouver Island in British Columbia.

Eastern red-tailed hawk (B. j. borealis)breeds from southeast Canada and Maine south through Texas and east to northern Florida.

Western red-tailed hawk (B. j. calurus)greatest longitudinal breeding distribution of any race of red-tailed hawk.

Central American red-tailed hawk (B. j. costaricensis)from Nicaragua to Panama.

Southwestern red-tailed hawk (B. j. fuertesi)breeds from northern Chihuahua to South Texas.

Tres Marias red-tailed hawk (B. j. fumosus)endemic to Islas Marías, Mexico.

Mexican Highlands red-tailed hawk (B. j. hadropus)native to the Mexican Highlands.

Harlan's hawk (B. j. harlani)breeds from central Alaska to northwestern Canada, with the largest number of birds breeding in the Yukon or western Alaska, reaching their southern limit in north-central British Columbia.

Red-tailed hawk (kemsiesi) (B. j. kemsiesi)a dark subspecies resident from Chiapas, Mexico, to Nicaragua.

Krider's hawk (B. j. kriderii)breeds from southern Alberta, southern Saskatchewan, southern Manitoba, and extreme western Ontario south to south-central Montana, Wyoming, western Nebraska, and western Minnesota.

Socorro red-tailed hawk (B. j. socorroensis)endemic to Socorro Island, Mexico.

Cuban red-tailed hawk (B. j. solitudinis)native to the Bahamas and Cuba.

Florida red-tailed hawk (B. j. umbrinus)occurs year-round in peninsular Florida north to as far Tampa Bay and the Kissimmee Prairie south throughout the rest of peninsular Florida south to the Florida Keys.

 

Description

Red-tailed hawk plumage can be variable, depending on the subspecies and the region. These color variations are morphs, and are not related to molting. The western North American population, B. j. calurus, is the most variable subspecies and has three main color morphs: light, dark, and intermediate or rufous. The dark and intermediate morphs constitute 10–20% of the population in the Western United States, but seem to constitute only 1–2% of B. j. calurus in western Canada. A whitish underbelly with a dark brown band across the belly, formed by horizontal streaks in feather patterning, is present in most color variations. This feature is variable in eastern hawks and generally absent in some light subspecies (i.e. B. j. fuertesi). Most adult red-tails have a dark-brown nape and upper head, which gives them a somewhat hooded appearance, while the throat can variably present a lighter brown "necklace". Especially in younger birds, the underside may be otherwise covered with dark-brown spotting, and some adults may too manifest this stippling. The back is usually a slightly darker brown than elsewhere with paler scapular feathers, ranging from tawny to white, forming a variable imperfect "V" on the back. The tail of most adults, which gives this species its name, is rufous brick-red above with a variably sized, black subterminal band and generally appears light buff-orange from below. In comparison, the typical pale immatures (i.e. less than two years old) typically have a mildly paler headed and tend to show a darker back than adults with more apparent pale wing-feather edges above (for descriptions of dark morph juveniles from B. j. calurus, which is also generally apt for description of rare dark morphs of other races, see under that subspecies description). In immature red-tailed hawks of all morphs, the tail is a light brown above with numerous small dark brown bars of roughly equal width, but these tend to be much broader on dark morph birds. Even in young red-tails, the tail may be a somewhat rufous tinge of brown. The bill is relatively short and dark, in the hooked shape characteristic of raptors, and the head can sometimes appear small in size against the thick body frame. The cere, the legs, and the feet of the red-tailed hawk are all yellow, as is the color of bare parts in many accipitrids of different lineages. Immature birds can be readily identified at close range by their yellowish irises. As the bird attains full maturity over the course of 3–4 years, the iris slowly darkens into a reddish-brown, which is the adult eye-color in all races. Seen in flight, adults usually have dark brown along the lower edge of the wings, against a mostly pale wing, which bares light brownish barring. Individually, the underwing coverts can range from all dark to off-whitish (most often more heavily streaked with brown) which contrasts with a distinctive black patagium marking. The wing coloring of adults and immatures is similar but for typical pale morph immatures having somewhat heavier brownish markings.

 

Though the markings and color vary across the subspecies, the basic appearance of the red-tailed hawk is relatively consistent.

 

Overall, this species is blocky and broad in shape, often appearing (and being) heavier than other Buteos of similar length. They are the heaviest Buteos on average in eastern North America, albeit scarcely ahead of the larger winged rough-legged buzzard (Buteo lagopus), and second only in size in the west to the ferruginous hawk (Buteo regalis). Red-tailed hawks may be anywhere from the fifth to the ninth heaviest Buteo in the world depending on what figures are used. However, in the northwestern United States, ferruginous hawk females are 35% heavier than female red-tails from the same area.[2] On average, western red-tailed hawks are relatively longer winged and lankier proportioned but are slightly less stocky, compact and heavy than eastern red-tailed hawks in North America. Eastern hawks may also have mildly larger talons and bills than western ones. Based on comparisons of morphology and function amongst all accipitrids, these features imply that western red-tails may need to vary their hunting more frequently to on the wing as the habitat diversifies to more open situations and presumably would hunt more variable and faster prey, whereas the birds of the east, which was historically well-wooded, are more dedicated perch hunters and can take somewhat larger prey but are likely more dedicated mammal hunters. In terms of size variation, red-tailed hawks run almost contrary to Bergmann's rule (i.e. that northern animals should be larger in relation than those closer to the Equator within a species) as one of the northernmost subspecies, B. j. alascensis, is the second smallest race based on linear dimensions and that two of the most southerly occurring races in the United States, B. j. fuertesi and B. j. umbrinus, respectively, are the largest proportioned of all red-tailed hawks. Red-tailed hawks tend have a relatively short but broad tails and thick, chunky wings. Although often described as long-winged, the proportional size of the wings is quite small and red-tails have high wing loading for a buteonine hawk. For comparison, two other widespread Buteo hawks in North America were found to weigh: 30 g (1.1 oz) for every square centimeter of wing area in the rough-legged buzzard (B. lagopus) and 44 g (1.6 oz)/cm2 in the red-shouldered hawk (B. lineatus). In contrast, the red-tailed hawk weighed considerably more for their wing area: 199 g (7.0 oz) per square cm.

 

As is the case with many raptors, the red-tailed hawk displays sexual dimorphism in size, as females are on average 25% larger than males. As is typical in large raptors, frequently reported mean body mass for red-tailed hawks is somewhat higher than expansive research reveals. Part of this weight variation is seasonal fluctuations; hawks tend to be heavier in winter than during migration or especially during the trying summer breeding season, and also due to clinal variation. Furthermore, immature hawks are usually lighter in mass than their adult counterparts despite having somewhat longer wings and tails. Male red-tailed hawks may weigh from 690 to 1,300 g (1.52 to 2.87 lb) and females may weigh 801 to 1,723 g (1.766 to 3.799 lb) (the lowest figure from a migrating female immature from Goshute Mountains, Nevada, the highest from a wintering female in Wisconsin). Some sources claim the largest females can weigh up to 2,000 g (4.4 lb), but whether this is in reference to wild hawks (as opposed to those in captivity or used for falconry) is not clear. The largest known survey of body mass in red-tailed hawks is still credited to Craighead and Craighead (1956), who found 100 males to average 1,028 g (2.266 lb) and 108 females to average 1,244 g (2.743 lb). However, these figures were apparently taken from labels on museum specimens, from natural history collections in Wisconsin and Pennsylvania, without note to the region, age, or subspecies of the specimens. However, 16 sources ranging in sample size from the aforementioned 208 specimens to only four hawks in Puerto Rico (with 9 of the 16 studies of migrating red-tails), showed that males weigh a mean of 860.2 g (1.896 lb) and females weigh a mean of 1,036.2 g (2.284 lb), about 15% lighter than prior species-wide published weights. Within the continental United States, typical weights of males can range from 840.8 g (1.854 lb) (for migrating males in Chelan County, Washington) to 1,031 g (2.273 lb) (for male hawks found dead in Massachusetts), and females ranged from 1,057.9 g (2.332 lb) (migrants in the Goshutes) to 1,373 g (3.027 lb) (for females diagnosed as B. j. borealis in western Kansas). Size variation in body mass reveals that the red-tailed hawk typically varies only a modest amount and that size differences are geographically inconsistent.[9][40]

 

Male red-tailed hawks can measure 45 to 60 cm (18 to 24 in) in total length, females measuring 48 to 65 cm (19 to 26 in) long. Their wingspan typically can range from 105 to 141 cm (3 ft 5 in to 4 ft 8 in), although the largest females may possible span up to 147 cm (4 ft 10 in). In the standard scientific method of measuring wing size, the wing chord is 325.1–444.5 mm (12.80–17.50 in) long. The tail measures 188 to 258.7 mm (7.40 to 10.19 in) in length. The exposed culmen was reported to range from 21.7 to 30.2 mm (0.85 to 1.19 in) and the tarsus averaged 74.7–95.8 mm (2.94–3.77 in) across the races. The middle toe (excluding talon) can range from 38.3 to 53.8 mm (1.51 to 2.12 in), with the hallux-claw (the talon of the rear toe, which has evolved to be the largest in accipitrids) measuring from 24.1 to 33.6 mm (0.95 to 1.32 in) in length.

 

Identification

Although they overlap in range with most other American diurnal raptors, identifying most mature red-tailed hawks to species is relatively straightforward, particularly if viewing a typical adult at a reasonable distance. The red-tailed hawk is the only North American hawk with a rufous tail and a blackish patagium marking on the leading edge of its wing (which is obscured only on dark morph adults and Harlan's hawks by similarly dark-colored feathers). Other larger adult Buteo spp. in North America usually have obvious distinct markings that are absent in red-tails, whether the rufous-brown "beard" of Swainson's hawks (B. swainsonii) or the colorful rufous belly and shoulder markings and striking black-and-white mantle of red-shouldered hawks (also the small "windows" seen at the end of their primaries).[ In perched individuals, even as silhouettes, the shape of large Buteo spp. may be distinctive, such as the wingtips overhanging the tail in several other species, but not in red-tails. North American Buteo spp. range from the dainty, compact builds of much smaller ones, such as broad-winged hawk (B. platypterus) to the heavyset, neckless look of ferruginous hawks or the rough-legged buzzards, which have a compact, smaller appearance than a red-tail in perched birds due to its small bill, short neck, and much shorter tarsi, while the opposite effect occurs in flying rough-legs with their much bigger wing area. In flight, most other large North American Buteo spp. are distinctly longer and more slender-winged than red-tailed hawks, with the much paler ferruginous hawk having peculiarly slender wings in relation to its massive, chunky body. Swainson's hawks are distinctly darker on the wing and ferruginous hawks are much paler-winged than typical red-tailed hawks. Pale morph adult ferruginous hawk can show mildly tawny-pink (but never truly rufous) upper tail, and like red-tails tend to have dark markings on underwing-coverts and can have a dark belly band, but compared to red-tailed hawks have a distinctly broader head, their remiges are much whiter looking with very small, dark primary tips, they lack the red-tail's diagnostic patagial marks and usually also lack the dark subterminal tail-band, and ferruginous hawks have totally feathered tarsi. With its whitish head, the ferruginous hawk is most similar to Krider's red-tailed hawks, especially in immature plumage, but the larger hawk has broader head and narrower wing shape, and the ferruginous immatures are paler underneath and on their legs. Several species share a belly band with the typical red-tailed hawk, but they vary from subtle (as in the ferruginous hawk) to solid blackish, the latter in most light-morph rough-legged buzzards. More difficult to identify among adult red-tails are their darkest variations, as most species of Buteo in North America also have dark morphs. Western dark morph red-tails (i.e. B. j. calurus) adults, however, retain the typical distinctive brick-red tail, which other species lack, and may stand out even more against the otherwise all chocolate-brown to black bird. Standard pale juveniles when perched show a whitish patch in the outer half of the upper surface of the wing, which other juvenile Buteo spp. lack.[ The most difficult to identify stages and plumage types are dark morph juveniles, Harlan's hawk and some Krider's hawks (the latter mainly with typical ferruginous hawks as mentioned). Some darker juveniles are similar enough to other Buteo juveniles that they "cannot be identified to species with any confidence under various field conditions." However, field identification techniques have advanced in the last few decades and most experienced hawk-watchers can distinguish even the most vexingly plumaged immature hawks, especially as the wing shapes of each species becomes apparent after seeing many. Harlan's hawks are most similar to dark morph rough-legged buzzards and dark morph ferruginous hawks. Wing shape is the most reliable identification tool for distinguishing Harlan's hawks from these, but also the pale streaking on the breast of Harlan's, which tends to be conspicuous in most individuals, and is lacking in the other hawks. Also, dark morph ferruginous hawks do not have the dark subterminal band of a Harlan's hawk, but do bear a black undertail covert lacking in Harlan's.

 

Vocalization

The cry of the red-tailed hawk is a 2- to 3-second, hoarse, rasping scream, variously transcribed as kree-eee-ar, tsee-eeee-arrr or sheeeeee, that begins at a high pitch and slurs downward. This cry is often described as sounding similar to a steam whistle. The red-tailed hawk frequently vocalizes while hunting or soaring, but vocalizes loudest and most persistently in defiance or anger, in response to a predator or a rival hawk's intrusion into its territory. At close range, it makes a croaking guh-runk, possibly as a warning sound. Nestlings may give peeping notes with a "soft, sleepy quality" that give way to occasional screams as they develop, but those are more likely to be a soft whistle rather than the harsh screams of the adults. Their latter hunger call, given from 11 days (as recorded in Alaska) to after fledgling (in California), is different, a two-syllabled, wailing klee-uk food cry exerted by the young when parents leave the nest or enter their field of vision. A strange mechanical sound "not very unlike the rush of distant water" has been reported as uttered in the midst of a sky-dance. A modified call of chirp-chwirk is given during courtship, while a low key, duck-like nasal gank may be given by pairs when they are relaxed.

 

The fierce, screaming cry of the adult red-tailed hawk is frequently used as a generic raptor sound effect in television shows and other media, even if the bird featured is not a red-tailed hawk. It is especially used in depictions of the bald eagle, which contributes to the common misconception that it is a bald eagle cry; actual bald eagle vocalizations are far softer and more chirpy than those of a red-tailed hawk.

 

Distribution and habitat

The red-tailed hawk is one of the most widely distributed of all raptors in the Americas. It occupies the largest breeding range of any diurnal raptor north of the Mexican border, just ahead of the American kestrel (Falco sparverius). While the peregrine falcon (Falco peregrinus) has a greater latitudinal distribution as a nester in North America, its range as a breeding species is far more sporadic and sparse than that of red-tailed hawks. The red-tailed hawk breeds from nearly north-central Alaska, the Yukon, and a considerable portion of the Northwest Territories, there reaching as far as a breeder as Inuvik, Mackenzie River Delta and skirting the southern shores of Great Bear Lake and Great Slave Lake. Thereafter in northern Canada, breeding red-tails continue to northern Saskatchewan and across to north-central Ontario east to central Quebec and the Maritime Provinces of Canada, and south continuously to Florida. No substantial gaps occur throughout the entire contiguous United States where breeding red-tailed hawks do not occur. Along the Pacific, their range includes all of Baja California, including Islas Marías, and Socorro Island in the Revillagigedo Islands. On the mainland, breeding red-tails are found continuously to Oaxaca, then experience a brief gap at the Isthmus of Tehuantepec thereafter subsequently continuing from Chiapas through central Guatemala on to northern Nicaragua. To the south, the population in highlands from Costa Rica to central Panama is isolated from breeding birds in Nicaragua. Further east, breeding red-tailed hawks occur in the West Indies in north Bahamas (i.e. Grand Bahama, Abaco and Andros) and all larger islands (such as Cuba, Jamaica, Hispaniola, and Puerto Rico) and into the northern Lesser Antilles (Virgin Islands, Saint Barthélemy, Saba, Saint Kitts, and Nevis, being rare as a resident on Saint Eustatius and are probably extinct on Saint Martin). Their typical winter range stretches from southern Canada south throughout the remainder of the breeding range.

 

Red-tailed hawks have shown the ability to become habituated to almost any habitat present in North and Central America. Their preferred habitat is mixed forest and field, largely woodland edge with tall trees or alternately high bluffs that may be used as nesting and perching sites. They occupy a wide range of habitats and altitudes, including deserts, grasslands, nearly any coastal or wetland habitat, mountains, foothills, coniferous and deciduous woodlands, and tropical rainforests. Agricultural fields and pastures, which are more often than not varied with groves, ridges, or streamside trees in most parts of America, may make nearly ideal habitat for breeding or wintering red-tails. They also adapt well to suburban areas especially ones with tall trees or any kind of parkland. Some red-tails may survive or even flourish in urban areas, usually hunting and roosting in available urban parks, cemeteries, road verges, and so on, and nesting freely either in trees or virtually any tall man-made structures. One famous urban red-tailed hawk, known as "Pale Male", became the subject of a nonfiction book, Red-Tails in Love: A Wildlife Drama in Central Park, and is the first known red-tail in decades to successfully nest and raise young in the crowded New York City borough of Manhattan. As studied in Syracuse, New York, the highway system has been very beneficial to red-tails as it juxtaposed trees and open areas and blocks human encroachment with fences, with the red-tailed hawks easily becoming acclimated to car traffic. The only practice that has a negative effect on the highway-occupying red-tails is the planting of exotic Phragmites, which may occasionally obscure otherwise ideal highway habitat.

 

In the northern Great Plains, the widespread practices of wildfire suppression and planting of exotic trees by humans has allowed groves of aspen and various other trees to invade what was once vast, almost continuous prairie grasslands, causing grassland obligates such as ferruginous hawks to decline and allowing parkland-favoring red-tails to flourish. To the contrary, clear-cutting of mature woodlands in New England, resulting in only fragmented and isolated stands of trees or low second growth remaining, was recorded to also benefit red-tailed hawks, despite being to the determent of breeding red-shouldered hawks. The red-tailed hawk, as a whole, rivals the peregrine falcon and the great horned owl among raptorial birds in the use of diverse habitats in North America. Beyond the high Arctic (as they discontinue as a breeder at the tree line), few other areas exist where red-tailed hawks are absent or rare in North and Central America. Some areas of unbroken forest, especially lowland tropical forests, rarely host red-tailed hawks, although they can occupy forested tropical highlands surprisingly well. In deserts, they can only occur where some variety of arborescent growth or ample rocky bluffs or canyons occur.

 

Behavior

The red-tailed hawk is highly conspicuous to humans in much of its daily behavior. Most birds in resident populations, which are well more than half of all red-tailed hawks, usually split nonbreeding-season activity between territorial soaring flight and sitting on a perch. Often, perching is for hunting purposes, but many sit on a tree branch for hours, occasionally stretching on a single wing or leg to keep limber, with no signs of hunting intent. Wintering typical pale-morph hawks in Arkansas were found to perch in open areas near the top of tall, isolated trees, whereas dark morphs more frequently perched in dense groups of trees. For many, and perhaps most, red-tailed hawks being mobbed by various birds is a daily concern and can effectively disrupt many of their daily behaviors. Mostly larger passerines, of multiple families from tyrant flycatchers to icterids, mob red-tails, despite other raptors, such as Accipiter hawks and falcons, being a notably greater danger to them. The most aggressive and dangerous attacker as such is likely to be various crows or other corvids, i.e. American crows (Corvus brachyrhynchos), because a mobbing group (or "murder") of them can number up to as many as 75 crows, which may cause grievous physical harm to a solitary hawk, and if the hawks are nesting, separate the parent hawks and endanger the eggs or nestlings within their nest to predation by crows. Birds that mob red-tailed hawks can tell how distended the hawk's crop is (i.e. the upper chest and throat area being puffy versus flat-feathered and sleek), thus mob more often when the hawk is presumably about to hunt.

 

Flight

In flight, this hawk soars with wings often in a slight dihedral, flapping as little as possible to conserve energy. Soaring is by far the most efficient method of flight for red-tailed hawks, so is used more often than not. Active flight is slow and deliberate, with deep wing beats. Wing beats are somewhat less rapid in active flight than in most other Buteo hawks, even heavier species such as ferruginous hawks tend to flap more swiftly, due to the morphology of the wings. In wind, it occasionally hovers on beating wings and remains stationary above the ground, but this flight method is rarely employed by this species. When soaring or flapping its wings, it typically travels from 32 to 64 km/h (20 to 40 mph), but when diving may exceed 190 km/h (120 mph). Although North American red-tailed hawks will occasionally hunt from flight, a great majority of flight by red-tails in this area is for non-hunting purpose. During nest defense, red-tailed hawks may be capable of surprisingly swift, vigorous flight, while repeatedly diving at perceived threats.

 

Migration

Red-tailed hawks are considered partial migrants, as in about the northern third of their distribution, which is most of their range in Canada and Alaska, they almost entirely vacate their breeding grounds. In coastal areas of the north, however, such as in the Pacific Northwest to southern Alaska and in Nova Scotia on the Atlantic, red-tailed hawks do not usually migrate. More or less, any area where snow cover is nearly continuous during the winter shows an extended absence of most red-tailed hawks, so some areas as far south as Montana may show strong seasonal vacancies of red-tails. In southern Michigan, immature red-tailed hawks tended to remain in winter only when voles were abundant. During relatively long, harsh winters in Michigan, many more young ones were reported in northeastern Mexico. To the opposite extreme, hawks residing as far north as Fairbanks, Alaska, may persevere through the winter on their home territory, as was recorded with one male over three consecutive years. Birds of any age tend to be territorial during winter but may shift ranges whenever food requirements demand it. Wintering birds tend to perch on inconspicuous tree perches, seeking shelter especially if they have a full crop or are in the midst of poor or overly windy weather. Adult wintering red-tails tend to perch more prominently than immatures do, which select lower or more secluded perches. Immatures are often missed in winter bird counts, unless they are being displaced by dominant adults. Generally, though, immatures can seem to recognize that they are less likely to be attacked by adults during winter and can perch surprisingly close to them. Age is the most significant consideration of wintering hawks' hierarchy, but size does factor in, as larger immatures (presumably usually females) are less likely to displaced than smaller ones. Dark adult red-tailed hawks appear to be harder to locate when perched than other red-tails. In Oklahoma, for example, wintering adult Harlan's hawks were rarely engaged in fights or chased by other red-tails. These hawks tended to gather in regional pockets and frequently the same ones occurred year-to-year. In general, migratory behavior is complex and reliant on each individual hawk's decision-making (i.e. whether prey populations are sufficient to entice the hawk to endure prolonged snow cover). During fall migration, departure may occur as soon as late September, but peak movements occur in late October and all of November in the United States, with migration ceasing after mid-December. The northernmost migrants may pass over resident red-tailed hawks in the contiguous United States, while the latter are still in the midst of brooding fledglings. Not infrequently, several autumn hawk watches in Ontario, Quebec, and the northern United States record 4,500–8,900 red-tailed hawks migrating through each fall, with records of up to 15,000 in a season at Hawk Ridge hawk watch in Duluth, Minnesota. Unlike some other Buteo spp., such as Swainson's hawks and broad-winged hawks, red-tailed hawks do not usually migrate in groups, instead passing by one-by-one, and only migrate on days when winds are favorable. Most migrants do not move past southern Mexico in late autumn, but a few North American migrants may annually move as far south as breeding red-tailed hawks happen to occur, i.e. in Central America to as far south Panama. However, a few records were reported of wintering migrant red-tails turning up in Colombia, the first records of them anywhere in South America. Spring northward movements may commence as early as late February, with peak numbers usually occurring in late March and early April. Seasonal counts may include up to 19,000 red-tails in spring at Derby Hill hawk watch, in Oswego, New York, sometimes more than 5,000 are recorded in a day there. The most northerly migratory individuals may not reach breeding grounds until June, even adults.

 

Immature hawks migrate later than adults in spring on average, but not, generally speaking, in autumn. In the northern Great Lakes, immatures return in late May to early June, when adults are already well into their nesting season and must find unoccupied ranges. In Alaska, adults tend to migrate before immatures in early to mid-September, to the contrary of other areas, probably as heavy snowfall begins. Yearlings that were banded in southwestern Idaho stayed for about 2 months after fledging, and then traveled long distances with a strong directional bias, with 9 of 12 recovered southeast of the study area- six of these moved south to coastal lowlands in Mexico] and as far as Guatemala, 4,205 km (2,613 mi) from their initial banding. In California, 35 hawks were banded as nestlings; 26 were recovered at less than 50 miles away, with multidirectional juvenile dispersals. Nestlings banded in Southern California sometimes actually traveled north as far as 1,190 km (740 mi) to Oregon, ranging to the opposite extreme as far as a banded bird from the Sierra Nevadas that moved 1,700 km (1,100 mi) south to Sinaloa. Nestlings banded in Green County, Wisconsin, did not travel very far comparatively by October–November, but by December, recoveries were found in states including Illinois, Iowa, Texas, Louisiana, and Florida.

 

Diet

The red-tailed hawk is carnivorous, and a highly opportunistic feeder. Nearly any small animal they encounter may be viewed as potential food. Their most common prey are small mammals such as rodents and lagomorphs, but they also consume birds, reptiles, fish, amphibians, and invertebrates. Prey varies considerably with regional and seasonal availability, but usually centers on rodents, accounting for up to 85% of a hawk's diet. In total, nearly 500 prey species have been recorded in their diet, almost as many as great horned owls have been recorded as taking. When 27 North American studies are reviewed, mammals make up 65.3% of the diet by frequency, 20.9% by birds, 10.8% by reptiles, 2.8% by invertebrates, and 0.2% by amphibians and fish. The geometric mean body mass of prey taken by red-tailed hawks in North America is about 187 g (6.6 oz) based on a pair of compilation studies from across the continent, regionally varying at least from 43.4 to 361.4 g (1.53 to 12.75 oz). Staple prey (excluding invertebrates) has been claimed to weigh from 15 to 2,114 g (0.033 to 4.661 lb), ranging roughly from the size of a small mouse or lizard to the size of a black-tailed jackrabbit (Lepus californicus). The daily food requirements range from 7 to 11.2% of their own body weight, so that about three voles or the equivalent weight are required daily for a typical range adult.

 

The talons and feet of red-tailed hawks are relatively large for a Buteo hawk; in an average-sized adult red-tail, the "hallux-claw" or rear talon, the largest claw on all accipitrids, averages about 29.7 mm (1.17 in). In fact, the talons of red-tails in some areas averaged of similar size to those of ferruginous hawks which can be considerably heavier and notably larger than those of the only slightly lighter Swainson's hawk. This species may exert an average of about 91 kg/cm2 (1,290 lbf/in2) of pressure through its feet. Owing to its morphology, red-tailed hawks generally can attack larger prey than other Buteo hawks typically can, and are capable of selecting the largest prey of up to their own size available at the time of hunting, though in all likelihood numerically most prey probably weighs on average about 20% of the hawk's own weight (as is typical of many birds of prey). Red-tailed hawks usually hunt by watching for prey activity from a high perch, also known as still hunting. Upon being spotted, prey is dropped down upon by the hawk. Red-tails often select the highest available perches within a given environment, since the greater the height they are at, the less flapping is required and the faster the downward glide they can attain toward nearby prey. If prey is closer than average, the hawk may glide at a steep downward angle with few flaps, if farther than average, it may flap a few swift wingbeats alternating with glides. Perch hunting is the most successful hunting method generally speaking for red-tailed hawks and can account for up to 83% of their daily activities (i.e. in winter). Wintering pairs may join and aseasonally may join forces to group hunt agile prey that they may have trouble catching by themselves, such as tree squirrels. This may consist of stalking opposites sides of a tree, to surround the squirrel and almost inevitably drive the rodent to be captured by one after being flushed by the other hawk.

 

The most common flighted hunting method for red-tail is to cruise around 10 to 50 m (33 to 164 ft) over the ground with flap-and-glide type flight, interspersed occasionally with harrier-like quarters over the ground. This method is less successful than perch hunting, but seems relatively useful for capturing small birds and may show the best results while hunting in hilly country. Hunting red-tailed hawks readily use trees, bushes, or rocks for concealment before making a surprise attack, even showing a partial ability to dodge among trees in an Accipiter-like fashion. Among thick stands of spruce in Alaska, a dodging hunting flight was thought to be unusually important to red-tails living in extensive areas of conifers, with hawks even coming to the ground and walking hurriedly in prey pursuit especially if the prey was large, a similar behavior to goshawks. Additional surprisingly swift aerial hunting has reported in red-tails that habitually hunt bats in Texas. Here, the bat-hunting specialists stooped with half-closed wings, quite falcon-like, plowing through the huge stream of bats exiting their cave roosts, then zooming upwards with a bat in its talons. These hawks also flew parallel closely to the stream, then veer sharply into it and seize a bat. In the neotropics, red-tails have shown the ability to dodge amongst forest canopy whilst hunting. In Kansas, red-tailed hawks were recorded sailing to catch flying insects, a hunting method more typical of a Swainson's hawk. Alternately, they may drop to the ground to forage for insects like grasshoppers and beetles as well as other invertebrates and probably amphibians and fish (except by water in the latter cases). Hunting afoot seems to be particularly prevalent among immatures. Young red-tailed hawks in northeastern Florida were recorded often extracting earthworms from near the surface of the ground and some had a crop full of earthworms after rains. Ground hunting is also quite common on Socorro Island, where no native land mammals occur, and invertebrates are more significant to their overall diet. A red-tailed hawk was observed to incorporate an unconventional killing method, which was drowning a heron immediately after capture. One red-tailed hawk was seen to try to grab a young ground squirrel and, upon missing it, screamed loudly, which in turn caused another young squirrel to break into a run, wherein it was captured. Whether this was an intentional hunting technique needs investigation. Upon capture, smaller prey is taken to a feeding perch, which is almost always lower than a hunting perch. Among small prey, rodents are often swallowed whole, as are shrews and small snakes, while birds are plucked and beheaded. Even prey as small as chipmunks may take two or three bites to consume. Larger mammals of transportable size are at times beheaded and have part of their fur discarded, then leftovers are either stored in a tree or fall to the ground. Large prey, especially if too heavy to transport on the wing, is often dragged to a secluded spot and dismantled in various ways. If they can successfully carry what remains to a low perch, they tend to feed until full and then discard the rest.

 

Mammals

Rodents are certainly the type of prey taken most often by frequency, but their contribution to prey biomass at nests can be regionally low, and the type, variety, and importance of rodent prey can be highly variable. In total, well over 100 rodent species have turned up the diet of red-tailed hawks. Rodents of extremely varied sizes may be hunted by red-tails, with species ranging in size from the 8.2 g (0.29 oz) eastern harvest mouse (Reithrodontomys humulis) to full grown muskrats (Ondatra zibethicus). At times, the red-tailed hawk is thought of as a semi-specialized vole-catcher, but voles are a subsistence food that is more or less taken until larger prey such as rabbits and squirrels can be captured. In an area of Michigan, immature hawks took almost entirely voles but adults were diversified feeders. Indeed, the 44.1 g (1.56 oz) meadow vole (Microtus pennsylvanicus) was the highest frequency prey species in 27 dietary studies across North America, accounting for up to 54% of the food at nests by frequency. It is quite rare for any one species to make up more than half of the food in any dietary study for red-tailed hawks. In total about 9 Microtus species are known in the overall diet, with 5 other voles and lemmings known to be included in their prey spectrum. Another well-represented species was the 27.9 g (0.98 oz) prairie vole (Microtus ochrogaster), which were the primary food, making up 26.4% of a sample of 1322, in eastern Kansas. While crepuscular in primary feeding activity, voles are known to be active both day and night, and so are reliable food for hawks than most non-squirrel rodents, which generally are nocturnal in activity. Indeed, most other microtine rodents are largely inaccessible to red-tailed hawks due to their strongly nocturnal foraging patterns, even though 24 species outside of voles and lemmings are known to be hunted. Woodrats are taken as important supplemental prey in some regions, being considerably larger than most other crictetid rodents, and some numbers of North American deermouse (Peromyscus maniculatus) may turn up. The largest representation of the latter species was contributing 11.9% of the diet in the Great Basin of Utah, making them the second best-represented prey species there. Considering this limited association with nocturnal rodents, the high importance of pocket gophers in the diet of red-tailed hawks is puzzling to many biologists, as these tend to be highly nocturnal and elusive by day, rarely leaving the confines of their burrow. At least 8 species of pocket gopher are included in the prey spectrum (not to mention 5 species of pocket mice). The 110 g (3.9 oz) northern pocket gopher (Thomomys talpoides) is particularly often reported and, by frequency, even turns up as the third most often recorded prey species in 27 American dietary studies. Presumably, hunting of pocket gophers by red-tails, which has possibly never been witnessed, occurs in dim light at first dawn and last light of dusk when they luck upon a gopher out foraging.

 

By far, the most important prey among rodents is squirrels, as they are almost fully diurnal. All told, nearly 50 species from the squirrel family have turned up as food. In particular, where they are distributed, ground squirrels are doubly attractive as a primary food source due to their ground-dwelling habits, as red-tails prefer to attack prey that is terrestrial. There are also many disadvantages to ground squirrels as prey: they can escape quickly to the security of their burrows, they tend to be highly social and they are very effective and fast in response to alarm calls, and a good deal of species enter hibernation that in the coldest climates can range up to a 6 to 9-month period (although those in warmer climates with little to no snowy weather often have brief dormancy and no true hibernation). Nonetheless, red-tailed hawks are devoted predators of ground squirrels, especially catching incautious ones as they go out foraging (which are often younger animals). A multi-year study conducted on San Joaquin Experimental Range in California, seemingly still the largest food study to date done for red-tailed hawks with 4031 items examined, showed that throughout the seasons the 722 g (1.592 lb) California ground squirrel (Otospermophilus beecheyi) was the most significant prey, accounting for 60.8% of the breeding season diet and about 27.2% of the diet for hawks year-around. Because of the extremely high density of red-tailed hawks on this range, some pairs came to specialize in diverse alternate prey, which consisted variously of kangaroo rats, lizards, snakes or chipmunks. One pair apparently lessened competition by focusing on pocket gophers instead despite being near the center of ground squirrel activity. In Snake River NCA, the primary food of red-tailed hawks was the 203.5 g (7.18 oz) Townsend's ground squirrel (Urocitellus townsendii), which made up nearly 21% of the food in 382 prey items across several years despite sharp spikes and crashes of the ground squirrel population there. The same species was the main food of red-tailed hawks in southeastern Washington, making up 31.2% of 170 items. An even closer predatory relationship was reported in the Centennial valley of Montana and south-central Montana, where 45.4% of 194 prey items and 40.2% of 261 items, respectively, of the food of red-tails consisted of the 455.7 g (1.005 lb) Richardson's ground squirrel (Urocitellus richardsonii). Locally in Rochester, Alberta, Richardson's ground squirrel, estimated to average 444 g (15.7 oz), were secondary in number to unidentified small rodents but red-tails in the region killed an estimated 22–60% of the area's ground squirrel, a large dent in the squirrel's population. Further east, ground squirrels are not so reliably distributed, but one study in southern Wisconsin, in one of several quite different dietary studies in that state, the 172.7 g (6.09 oz) thirteen-lined ground squirrel (Ictidomys tridecemlineatus) was the main prey species, making up 29.7% of the diet (from a sample of 165).

 

In Kluane Lake, Yukon, 750 g (1.65 lb) Arctic ground squirrels (Spermophilus parryii) were the main overall food for Harlan's red-tailed hawks, making up 30.8% of a sample of 1074 prey items. When these ground squirrels enter their long hibernation, the breeding Harlan's hawks migrate south for the winter. Nearly as important in Kluane Lake was the 200 g (7.1 oz) American red squirrel (Tamiasciurus hudsonicus), which constituted 29.8% of the above sample. Red squirrels are highly agile dwellers on dense spruce stands, which has caused biologists to ponder how the red-tailed hawks are able to routinely catch them. It is possible that the hawks catch them on the ground such as when squirrels are digging their caches, but theoretically, the dark color of the Harlan's hawks may allow them to ambush the squirrels within the forests locally more effectively. While American red squirrels turn up not infrequently as supplementary prey elsewhere in North America, other tree squirrels seem to be comparatively infrequently caught, at least during the summer breeding season. It is known that pairs of red-tailed hawks will cooperatively hunt tree squirrels at times, probably mostly between late fall and early spring. Fox squirrels (Sciurus niger), the largest of North America's tree squirrels at 800 g (1.8 lb), are relatively common supplemental prey but the lighter, presumably more agile 533 g (1.175 lb) eastern gray squirrel (Sciurus carolinensis) appears to be seldom caught based on dietary studies. While adult marmot may be difficult for red-tailed hawks to catch, young marmots are readily taken in numbers after weaning, such as a high frequency of yellow-bellied marmot (Marmota flaviventris) in Boulder, Colorado. Another grouping of squirrels but at the opposite end of the size spectrum for squirrels, the chipmunks are also mostly supplemental prey but are considered more easily caught than tree squirrels, considering that they are more habitual terrestrial foragers In central Ohio, eastern chipmunks (Tamias striatus), the largest species of chipmunk at an average weight of 96 g (3.4 oz), were actually the leading prey by number, making up 12.3% of a sample of 179 items.

 

Outside of rodents, the most important prey for North American red-tailed hawks is rabbits and hares, of which at least 13 species are included in their prey spectrum. By biomass and reproductive success within populations, these are certain to be their most significant food source (at least in North America). Adult Sylvilagus rabbits known to be hunted by red-tails can range from the 700 g (1.5 lb) brush rabbit (Sylvilagus bachmani) to the Tres Marias rabbit (Sylvilagus graysoni) at 1,470 g (3.24 lb) while all leporids hunted may range the 421.3 g (14.86 oz) pygmy rabbit (Brachylagus idahoensis) to hares and jackrabbits potentially up twice the hawk's own weight. While primarily crepuscular in peak activity, rabbits and hares often foraging both during day and night and so face almost constant predatory pressure from a diverse range of predators. Male red-tailed hawks or pairs which are talented rabbit hunters are likely to have higher than average productivity due to the size and nutrition of the meal ensuring healthy, fast-growing offspring. Most widely reported are the cottontails, which the three most common North America varieties softly grading into mostly allopatric ranges, being largely segregated by habitat preferences where they overlap in distribution. Namely, in descending order of reportage were: the eastern cottontail (Sylvilagus floridanus), the second most widely reported prey species overall in North America and with maximum percentage known in a given study was 26.4% in Oklahoma (out of 958 prey items), the mountain cottontail (Sylvilagus nuttallii), maximum representation being 17.6% out of a sample of 478 in Kaibab Plateau, Arizona and the desert cottontail (Sylvilagus audubonii), maximum representation being 22.4% out of a sample of 326 in west-central Arizona. Black-tailed jackrabbits (Lepus californicus) are even more intensely focused upon as a food source by the hawks found in the west, particularly the Great Basin. With the weight around 2,114 g (4.661 lb), adults of this species is the largest prey routinely hunted by red-tailed hawks. When jackrabbit numbers crash, red-tailed hawk productivity tends to decline as well. In northern Utah, black-tailed jackrabbits made up 55.3% of a sample of 329. Elsewhere, they are usually somewhat secondary by number.

 

In the boreal forests of Canada and Alaska, red-tails are fairly dependent on the snowshoe hare (Lepus americanus), falling somewhere behind the great horned owl and ahead of the Anerican goshawk in their regional reliance on this food source. The hunting preferences of red-tails who rely on snowshoe hares are variable. In Rochester, Alberta, 52% of snowshoe hares caught were adults, such prey estimated to average 1,287 g (2.837 lb), and adults, in some years, were six times more often taken than juvenile hares, which averaged an estimated 560 g (1.23 lb). 1.9–7.1% of adults in the regional population of Rochester were taken by red-tails, while only 0.3–0.8 of juvenile hares were taken by them. Despite their reliance on it, only 4% (against 53.4% of the biomass) of the food by frequency here was made up of hares. On the other hand, in Kluane Lake, Yukon, juvenile hares were taken roughly 11 times more often than adults, despite the larger size of adults here, averaging 1,406.6 g (3.101 lb), and that the overall prey base was less diverse at this more northerly clime. In both Rochester and Kluane Lake, the number of snowshoe hares taken was considerably lower than the number of ground squirrels taken. The differences in average characteristics of snowshoe hares that were hunted may be partially due to habitat (extent of bog openings to dense forest) or topography. Another member of the Lagomorpha order has been found in the diet include juvenile white-tailed jackrabbit (Lepus townsendii) and the much smaller American pika (Ochotona princeps), at 150 g (5.3 oz).

 

A diversity of mammals may be consumed opportunistically outside of the main food groups of rodents and leporids, but usually occur in low numbers. At least five species each are taken of shrews and moles, ranging in size from their smallest mammalian prey, the cinereus (Sorex cinereus) and least shrews (Cryptotis parva), which both weigh about 4.4 g (0.16 oz), to Townsend's mole (Scapanus townsendii), which weighs about 126 g (4.4 oz). A respectable number of the 90 g (3.2 oz) eastern mole (Scalopus aquaticus) were recorded in studies from Oklahoma and Kansas. Four species of bat have been recorded in their foods. The red-tailed hawks local to the large cave colonies of 12.3 g (0.43 oz) Mexican free-tailed bats (Tadarida brasiliensis) in Texas can show surprising agility, some of the same hawks spending their early evening and early morning hours in flight patrolling the cave entrances in order to stoop suddenly on these flighted mammals. Larger miscellaneous mammalian prey are either usually taken as juveniles, like the nine-banded armadillo (Dasypus novemcinctus), or largely as carrion, like the Virginia opossum (Didelphis virginiana). Small carnivorans may be taken, usually consisting of much smaller mustelids, like the least weasels (Mustela nivalis), stoats (Mustela erminea), and long-tailed weasels (Neogale frenata). slightly larger carnivores, such as small Indian mongooses (Herpestes auropunctatus), ringtails (Bassariscus astutus), small American minks (Neovison vison) and even adult striped skunk (Mephitis mephitis), which can be much larger than a fully grown hawk, was reportedly taken by red-tailed hawks. Additionally, red-tailed hawks are considered as potential predators of white-nosed coati (Nasua narica) and kit fox (Vulpes macrotis) Remains of exceptionally large carnivoran species, such as domestic cats (Felis catus), red fox ( Vulpes vulpes) and common raccoon (Procyon lotor) are sometimes found amongst their foods, but most are likely taken as juveniles or consumed only as carrion. Many of these medium-sized carnivorans are probably visited as roadkill, especially during the sparser winter months, but carrion has turned up more widely than previously thought. Some nests have been found (to the occasional "shock" of researchers) with body parts from large domestic stock like sheep (Ovis aries), pigs (Sus domesticus), horses (Equus caballus ) and cattle (Bos taurus) (not to mention wild varieties like deer), which red-tails must visit when freshly dead out on pastures and take a couple of talonfuls of meat. In one instance, a red-tailed hawk was observed to kill a small but seemingly healthy lamb. These are born heavier than most red-tails at 1,500 g (3.3 lb) but in this case, the hawk was scared away before it could consume its kill by the rifle fire of the shepherd who witnessed the instance.

 

Birds

Like most (but not all) Buteo hawks, red-tailed hawks do not primarily hunt birds in most areas, but can take them fairly often whenever they opportune upon some that are vulnerable. Birds are, by far, the most diverse class in the red-tailed hawk's prey spectrum, with well over 200 species known in their foods In most circumstances where birds become the main food of red-tailed hawks, it is in response to ample local populations of galliforms. As these are meaty, mostly terrestrial birds which usually run rather than fly from danger (although all wild species in North America are capable of flight), galliforms are ideal avian prey for red-tails. Some 23 species of galliforms are known to be taken by red-tailed hawks, about a third of these being species introduced by humans. Native quails of all five North American species may expect occasional losses. All 12 species of grouse native to North America are also occasionally included in their prey spectrum. In the state of Wisconsin, two large studies, from Waupun and Green County, found the main prey species to be the ring-necked pheasant (Phasianus colchicus), making up 22.7% of a sample of 176 and 33.8% of a sample of 139, respectively. With a body mass averaging 1,135 g (2.502 lb), adult pheasants are among the largest meals that male red-tails are likely to deliver short of adult rabbits and hares and therefore these nests tend to be relatively productive. Despite being not native to North America, pheasants usually live in a wild state. Chickens (Gallus gallus domesticus) are also taken throughout North America, with all Wisconsin studies also found large numbers of them, making up as much as 14.4% of the diet. Many studies reflect that free-ranging chickens are vulnerable to red-tailed hawks although somewhat lesser numbers are taken by them overall in comparison to nocturnal predators (i.e. owls and foxes) and goshawks. In Rochester, Alberta, fairly large numbers of ruffed grouse (Bonasa umbellus) were taken but relatively more juveniles were taken of this species than the two other main contributors to biomass here, snowshoe hare and Townsend's ground squirrel, as they are fairly independent early on and more readily available. Here the adult grouse was estimated to average 550 g (1.21 lb) against the average juvenile which in mid-summer averaged 170 g (6.0 oz).

 

Beyond galliforms, three other quite different families of birds make the most significant contributions to the red-tailed hawk's avian diet. None of these three families are known as particularly skilled or swift fliers, but are generally small enough that they would generally easily be more nimble in flight. One of these are the woodpeckers, if only for one species, the 131.6 g (4.64 oz) northern flicker (Colaptes auratus), which was the best represented bird species in the diet in 27 North American studies and was even the fourth most often detected prey species of all. Woodpeckers are often a favorite in the diet of large raptors as their relatively slow, undulating flight makes these relatively easy targets. The flicker in particular is a highly numerous species that has similar habitat preferences to red-tailed hawks, preferring fragmented landscapes with trees and openings or parkland-type wooded mosaics, and often forage on the ground for ants, which may make them even more susceptible. Varied other woodpecker species may turn up in their foods, from the smallest to the largest extant in North America, but are much more infrequently detected in dietary studies. Another family relatively often selected prey family are corvids, which despite their relatively large size, formidable mobbing abilities and intelligence are also slower than average fliers for passerines. 14 species of corvid are known to fall prey to red-tailed hawks. In the Kaibab Plateau, the 128 g (4.5 oz) Steller's jay (Cyanocitta stelleri) were the fourth most identified prey species (10.3% of the diet). 453 g (0.999 lb) American crows are also regularly detected supplemental prey in several areas. Even the huge common raven (Corvus corax), at 1,050 g (2.31 lb) at least as large as red-tailed hawk itself, may fall prey to red-tails, albeit very infrequently and only in a well-staged ambush. One of the most surprising heavy contributors are the icterids, despite their slightly smaller size and tendency to travel in large, wary flocks, 12 species are known to be hunted. One species pair, the meadowlarks, are most often selected as they do not flock in the same ways as many other icterids and often come to the ground, throughout their life history, rarely leaving about shrub-height. The 100.7 g (3.55 oz) western meadowlark (Sturnella neglecta), in particular, was the third most often detected bird prey species in North America. Red-winged blackbirds (Agelaius phoeniceus) which are probably too small, at an average weight of 52.4 g (1.85 oz), and fast for a red-tailed hawk to ever chase on the wing (and do travel in huge flocks, especially in winter) are nonetheless also quite often found in their diet, representing up to 8% of the local diet for red-tails. It is possible that males, which are generally bold and often select lofty perches from which to display, are most regularly ambushed. One bird species that often flocks with red-winged blackbirds in winter is even better represented in the red-tail's diet, the non-native 78 g (2.8 oz) European starling (Sturnus vulgaris), being the second most numerous avian prey species and seventh overall in North America. Although perhaps most vulnerable when caught unaware while calling atonally on a perch, a few starlings (or various blackbirds) may be caught by red-tails which test the agile, twisting murmurations of birds by flying conspicuously towards the flock, to intentionally disturb them and possibly detect lagging, injured individual birds that can be caught unlike healthy birds. However, this behavior has been implied rather than verified.

 

Over 50 passerine species from various other families beyond corvids, icterids and starlings are included in the red-tailed hawks' prey spectrum but are caught so infrequently as to generally not warrant individual mention. Non-passerine prey taken infrequently may include but are not limited to pigeons and doves, cuckoos, nightjars, kingfishers and parrots. However, of some interest, is the extreme size range of birds that may be preyed upon. Red-tailed hawks in Caribbean islands seem to catch small birds more frequently due to the paucity of vertebrate prey diversity here.

I had never tried this technique before, I spent about 10 minutes doing this, it's a wonderful technique

 

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Orange and Green never used a Korg MS20 Legacy controller before so they sit and watch as Red helps Clear sweep the Frequency knob.

collage on cardboard / 2011

FM4 Frequency Festival Besucher

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me voy a amplificar,

soy una frecuencia,

con un millon de megaheartz... ♫

 

[Zoe - reptilectric - Ultimos dias]

The first day of diversions in Beeston coincided with no less than three spare buses appearing on the 36, which considering there’s a fully orange allocation on the route most days is something quite remarkable. I think the 36 must have its normal daily boards allocated from Parliament Street before the 35 does, as the two routes share a set of vehicles and most of the time the 36 gets a full contingent of branded buses while the 35 ends up with a couple of spares. A lucky day on the 36 is when there’s one spare, let alone three!

 

Even better was that we got variety among the spare buses too, with one biogas, one silver E400 and a special liveried E400. Sure, it was one I’ve seen before instead of one of the ones I actually need, but 603 provides a splash of colour as it makes its way up Meadow Lane, Chilwell, with a diverted 36 on 5.8.24

 

An unfortunate by-product of the diversion was that Station Road in Beeston has become something of a pinch-point, probably not helped by the stupid decision to close part of Wollaton Road at the same time. Traffic gets backed up, and the 36s and indigos get bunched up just as they did during the tram works. The current 12-minute frequency had actually solved the bunching issues that plagued the 36 throughout the 2010s, but the roadworks have brought the problems right back. The lower frequency now means that two 36s bunching together leaves a 24+ minute gap in the service, which simply isn’t acceptable.

 

YP63 WFC

 

Liberty Walk Lamborghini Aventador LP700 with Fi Exhaust

 

More: www.fi-exhaust.com/

TEL : +886-2-26188966

Email : info@fi-exhaust.com

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"Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time. On some of the rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs. I am haunted by waters."

 

-Norman Maclean, "A River Runs Through It"

TodaysArt 2015

Pier, Scheveningen

 

Dmitry Gelfand (b.1974, St. Petersburg, Russia) and Evelina Domnitch (b. 1972, Minsk, Belarus) create sensory immersion environments that merge physics, chemistry and computer science with philosophy. Gelfand and Domnitch use wave phenomena to investigate questions of perception and infinity. They research these topics because science, which serves as the basis for contemporary thought, cannot fully explain how consciousness works. Domnitch and Gelfand’s installations have done away with ‘fixed’ art, such as recordings, and use continuously transforming phenomena instead. These phenomena take place directly in front of the observer and often serve to vastly extend the observer’s senses. Gelfand and Domnitch present their works “Implosion Chamber” and “Photonic Wind: shining into a vacuum chamber”. “Implosion Chamber” consists of high frequency sound waves going through a water-filled cylinder, causing naturally diffused air bubbles to implode. While revealing the motion imparted by sound waves, these implosions are accompanied by shock waves, supersonic liquid jet formations, temperatures as high as are found on the Sun, and conjecturably, quantum vacuum radiation. In the installation “Photonic Wind”, an Yves Klein blue laser beam levitates and propels diamond micropowder in a vacuum chamber. Forming starry jets and languorous vortical clouds, the diamond dust evokes the flow of light.

We know that all Prime numbers, after 2 and 5, end with either a 1, 3, 7 or 9 as their last digit.

If we look at the frequency of individual last digits we can see that 1, 3, 7, or 9 more or less occur at a similar frequency. However, as soon as we look at the frequency of the same last digit occurring twice in a row, we find that this is far less common and even less common for the same last digit occurring three times in a row.

 

Kannan Soundararajan and Robert Lemke-Oliver produced a paper in March 2016 on this apparent bias which received considerable attention in mathematical journals www.quantamagazine.org/mathematicians-discover-prime-cons.... If you really want to dive into the maths, the full paper can be found here arxiv.org/pdf/1709.06168.pdf .

 

March 3rd

Greenhouse heater "on" frequency

Work Fun

maps.secondlife.com/secondlife/The%20Frequency/190/164/1008

Grey Lamborghini Huracan LP580 with Fi Exhaust !

 

More: www.fi-exhaust.com/

TEL : +886-2-22979999

Email : info@fi-exhaust.com

I found this old gem in a flea market near Ipoh old town couple of weeks back. Pretty cool retro looking radio though and it's still in pristine condition. Wonder if it's still working as the original box and user manual are still intact.

 

View On Black

Labels are written in german because it was exported to former East-Germany...

Fleet number 609 was captured at the east end of Princes Street operating the second of the four evening peak services on the 44 which extend beyond the eastern terminus at Wallyford to Whitecraig. The cross city 44 between Balerno and Wallyford operates at a 12 minute frequency for most of the day during the week (less in the evenings and on Sats/Suns). 609 is seen against a background of the floodlit Balmoral Hotel with its 190 ft high (58m) clock tower, a notable Edinburgh landmark. On the south side of the street, Lothian 621 waits to get access to the stop at the top of the Waverley Steps, one of four entrances to Edinburgh’s principal station, Waverley. 621 is operating a Part Route 25 westwards to Sighthill

Lockheed Martin’s sixth Advanced Extremely High Frequency (AEHF-6) protected communications satellite is encapsulated in its protective fairings ahead of its expected March 26 launch on a United Launch Alliance Atlas V rocket. AEHF-6 is part of the AEHF system -- a resilient satellite constellation with global coverage and a sophisticated ground control system -- that provides global, survivable, protected communications capabilities for national leaders and tactical warfighters operating across ground, sea and air platforms. The anti-jam system also serves international allies to include Canada, the Netherlands, United Kingdom and Australia. For more information, visit: www.lockheedmartin.com/aehf

(Photo credit: United Launch Alliance)

 

vector control AC frequency inverters (VSD drives) on musical fountain for precision control: high response time.

 

Visit this location at Echoes, Metaphysics of frequencies in Second Life

After an electric second year the award-winning Sea Dance Festival 2016 is set to return to the most beautiful beach in Europe, Jaz Beach, Montenegro between 14th and 16th July 2016.

Voted best European medium-sized festival, Sea Dance has proven much within just two short years. Situated on Jaz beach named 'Europe's Best Beach' by Lonely Planet for its long sandy cove and picturesque mountains, white, turquoise and green shoreline and it's location near the historic town of Budva in Montenegro - it makes an ideal host for an array of world-class performers. 110,000 visitors descended on beautiful Jaz Beach to witness a visual and audible feast, Sea Dance added up to 300,000 visitors to the Exit Adventure, a unique festival holiday package comprised of two festivals in two neighbouring countries, whose first part is the globally acclaimed Exit Festival in Serbia.

Having recently secured a guaranteed ten further years at Jaz Beach, Sea Dance, near the historic town of Budva, and indeed Montenegro is Europe's hottest new festival destination and a must-visit for any music fan.

Stunning locations, world renowned artists and outstanding productions make Sea Dance Festival 2016 a must see.

Sea Dance is the coastal sister of EXIT music festival. Montenegro's incredible Jaz Beach hosts an all-star lineup of international acts, with the Adriatic ocean providing a breathtaking backdrop.

Officially Europe's 'Best Medium-Sized Festival', Sea Dance shores up a unique atmosphere, combining electronic artists with pop, urban and even the odd splash of reggae.

Sea Dance creates an eclectic, more upbeat festival alternative to other beach-based weekends, ensuring the EXIT team continue to blaze the trail for the whole of the continent.

 

Location-

Jaz Beach

Budva

Montenegro

Over the last few years Jaz Beach has become one of the most popular event and holiday spots in Montenegro. It's among the longest beaches in the country, and has great travel connections from Budva, which is around 25km east of the beach.

 

Line Up-

Skrillex, Andy C, Banco de Gaia, Black Coffee, Hurts, Jeff Mills, Lost Frequencies, Sister Bliss - Faithless DJ Set, Stereo MC's, Filatov & Karas, Goldie, Haris, Kristijan Molnar, Lea Dobričić, Miss Sunshine, Mladen Tomić, My Nu Leng, S.A.R.S., Shy FX feat. Stamina MC, Sub Focus & MC ID, Who See, Zomboy

+ MANY MANY MANY MORE TO COME dancegeo.com/event/sea-dance-festival-2016/

Conceptual Holographic Comms

 

© Wayman 2014

Photoshoot with Carla (carlachioreanu18),

Elizabeth Line,

Tottenham Court Road Station,

London.

 

Edited.

 

The Elizabeth line is a high-frequency hybrid urban–suburban rail service in London and its suburbs. It runs services on dedicated infrastructure in central London from the Great Western Main Line west of Paddington station to Abbey Wood and via Whitechapel to the Great Eastern Main Line near Stratford; along the Great Western Main Line to Reading and Heathrow Airport in the west; and along the Great Eastern Main Line to Shenfield in the east. The service is named after Queen Elizabeth II, who officially opened the line on 17 May 2022 during her Platinum Jubilee year; passenger services started on 24 May 2022.

 

Under the project name of Crossrail, the system was approved in 2007, and construction began in 2009. Originally planned to open in 2018, the project was repeatedly delayed, including for several months as a result of the COVID-19 pandemic.

 

In May 2015, existing commuter services on a section of one of the eastern branches, between Liverpool Street and Shenfield, were transferred to TfL Rail; this precursor service also took control of Heathrow Connect in May 2018, and some local services on the Paddington to Reading line in December 2019. These services were augmented by a new central section in May 2022, and rebranded as the Elizabeth line. The outer services were connected to the central section in November 2022. By May 2023, the central section will have up to 24 nine-carriage Class 345 trains per hour in each direction.

  

Mount Rainier reflected on Tipsoo lake. 5 bracket HDR. Nikkor 16-35 @ f22.

Selects of the 2016 Coachella Valley Music and Arts Festival (Saturday - Weekend 1)

 

feat.

The Dead Ships

Ex Hex

The Black Madonna

Strangers You Know

Lost Frequencies

James Bay

Rhye

CHVRCHES

Disclosure (feat. Sam Smith)

Ice Cube (feat. NWA, O'Shea Jackson Jr., WC, Snoop Dogg)

Guns N' Roses

Zhu (feat. Bone Thugs N' Harmony)

and so much more!

Beno Graphics

 

Selects of the 2016 Coachella Valley Music and Arts Festival (Saturday - Weekend 1)

 

feat.

The Dead Ships

Ex Hex

The Black Madonna

Strangers You Know

Lost Frequencies

James Bay

Rhye

CHVRCHES

Disclosure (feat. Sam Smith)

Ice Cube (feat. NWA, O'Shea Jackson Jr., WC, Snoop Dogg)

Guns N' Roses

Zhu (feat. Bone Thugs N' Harmony)

and so much more!

Selects of the 2016 Coachella Valley Music and Arts Festival (Saturday - Weekend 1)

 

feat.

The Dead Ships

Ex Hex

The Black Madonna

Strangers You Know

Lost Frequencies

James Bay

Rhye

CHVRCHES

Disclosure (feat. Sam Smith)

Ice Cube (feat. NWA, O'Shea Jackson Jr., WC, Snoop Dogg)

Guns N' Roses

Zhu (feat. Bone Thugs N' Harmony)

and so much more!

 

vector control variable speed drives (frequency converters), for motor control, energy saving and motion control

 

Senior Airman Dustin Harris, left, and 1st Lt. John Day, center, discuss radio frequencies with a Soldier assigned to the 82nd Airborne Division during an exercise in frequency hopping at Fort Bragg, N.C. Frequency hopping is changing regular frequencies during transmission, a radio operation technique that ensures secrecy and protects against communication channel jamming. Day and Harris are tactical air control party members with the 14th Air Support Operations Squadron. (U.S. Air Force photo by Airman 1st Class Alexander W. Riedel)

 

“If you want to find the secrets of the universe, think in terms of energy, frequency and vibration.”

 

Nikola Tesla

 

up: 2016/01/10

Generative pattern