Zahoor-Salmi
Golden eagle
Territoriality is believed to be the primary cause of interactions and confrontations between non-paired golden eagles. Golden eagles maintain some of the largest known home ranges (or territories) of any bird species but there is much variation of home range size across the range, possibly dictated by food abundance and habitat preference. Home ranges in most of the range can vary from 20 to 200 km2 (7.7 to 77.2 sq mi). In San Diego County in California, the home ranges varied from 49 to 137 km2 (19 to 53 sq mi), with an average of 93 km2 (36 sq mi). However, some home ranges have been much smaller, such as in southwestern Idaho where, possibly due to an abundance of jackrabbits, home ranges as small as 4.85 km2 (1.87 sq mi) are maintained. The smallest known home ranges on record for golden eagles are in the Bale Mountains of Ethiopia, where they range from 1.5 to 9 km2 (0.58 to 3.47 sq mi). 46% of undulating displays in Montana occurred shortly after the juvenile eagles left their parents range, suggesting that some residents defend and maintain territories year-round. Elsewhere it is stated that home ranges are less strictly maintained during winter but hunting grounds are basically exclusive. In Israel and Scotland, aggressive encounters peaked from winter until just before egg-laying and were less common during the nesting season. Threat displays include undulating flight and aggressive direct flapping flight with exaggerated downstrokes. Most displays by mature golden eagles (67% for males and 76% for females) occur, rather than around the nest, at the edge of their home ranges. In Western Norway, most recorded undulating flight displays occur during the pre-laying period in late winter/early spring.
Display flights seem to be triggered by the presence of other golden eagles. The use of display flights has a clear benefit in that it lessens the need for physical confrontations, which can be fatal. Usually, non-breeding birds are treated aggressively by the golden eagle maintaining their home range, normally being chased to the apparent limit of the range but with no actual physical contact. The territorial flight of the adult golden eagle is sometimes preceded or followed by intense bouts of undulating displays. The invader often responds by rolling over and presenting talons to the aggressor. Rarely, the two eagles will lock talons and tumble through the air; sometimes fall several revolutions and in some cases even tumble to the ground before releasing their grip. In some parts of the Alps, the golden eagle population has reached the saturation point in appropriate habitat and apparently violent confrontations are more common than in other parts of the range. Golden eagles may express their aggression via body language while perched, typically the adult female when confronted by an intruding eagle: the head and body are upright, feathers on head and neck are erect; the wings may be slightly spread and beak open; often accompanied by intense gaze. They then often engage in a similar posture with wings spread wide and oriented toward the threat; sometimes rocking back on tail and even flopping over onto the back with talons extended upward as defense. Such behavior may be accompanied by wing slap against the threatening intruder. When approached by an intruder, the defending eagle turns away, partially spreads tail, lowers head, and remains still; adults on the nest may lower head and “freeze” when approached by a person or a helicopter. Females in Israel displayed more than males and mostly against interspecific intruders; males apparently displayed primarily as part of courtship. Five of 7 aggressive encounters at carcasses during winter in Norway were won by females; in 15 of 21 conflicts, the younger bird dominated an older conspecific. However, obvious juvenile eagles (apparent to the adult eagles due to the amount of white on their wings and tail) are sometimes allowed to penetrate deeply into a pair’s home range and all parties commonly ignore each other. In North Dakota, it was verified that parent eagles were not aggressive towards their own young after the nesting period and some juveniles stayed on their parents territory until their 2nd spring and then left by their own accord.
Natural sources of mortality are largely reported in anecdotes. On rare occasions, golden eagles have been killed by competing predators or by hunting mammalian carnivores, including the aforementioned wolverine, snow leopard, cougar, brown bear and white-tailed eagle attacks. Most competitive attacks resulting in death probably occur at the talons of other golden eagles. Nestlings and fledglings are more likely to be killed by another predator than free-flying juveniles and adults. It has been suspected that golden eagle nests may be predated more frequently by other predators (especially birds, which are often the only other large animals that can access a golden eagle nest without the assistance of man-made climbing equipment) in areas where golden eagles are regularly disturbed at the nest by humans. Jeff Watson believed that common raven occasionally eats golden eagle eggs but only in situations where the parent eagles have abandoned their nesting attempt. However, there are no confirmed accounts of predation by other bird species on golden eagle nests. Occasionally, golden eagles may be killed by their prey in self-defense. There is an account of a golden eagle dying from the quills of a North American porcupine (Erethizon dorsatum) it had attempted to hunt. On the Isle of Rùm in Scotland, there are few cases of red deer trampling golden eagles to death, probably the result of a hind having intercepted a bird that was trying to kill a fawn. Although usually well out-matched by the predator, occasionally other large birds can put up a formidable fight against a golden eagle. An attempted capture of a great blue heron by a golden eagle resulted in the death of both birds from wounds sustained in the ensuing fight. There is at least one case in Scotland of a golden eagle dying after being “oiled” by a northern fulmar, a bird whose primary defense against predators is to disgorge an oily secretion which may inhibit the predator's ability to fly. Of natural sources of death, starvation is probably under-reported. 11 of 16 dead juvenile eagles which had hatched in Denali National Park had died of starvation. Of 36 deaths of golden eagles in Idaho, 55% were possibly attributable to natural causes, specifically 8 (26%) from unknown trauma, 3 (10%) from disease and 6 (19%) from unknown causes. Of 266 golden eagle deaths in Spain, only 6% were from unknown causes that could not directly attributed to human activities. Avian cholera caused by bacteria (Pasteurella multocida) infects eagles that eat waterfowl that have died from the disease. The protozoan Trichomonas sp. caused the deaths of 4 fledglings in a study of wild golden eagles in Idaho. Several further diseases that contribute to golden eagle deaths have been examined in Japan. A captive eagle died from two malignant tumors – one in the liver and one in the kidney.
Golden eagle
Territoriality is believed to be the primary cause of interactions and confrontations between non-paired golden eagles. Golden eagles maintain some of the largest known home ranges (or territories) of any bird species but there is much variation of home range size across the range, possibly dictated by food abundance and habitat preference. Home ranges in most of the range can vary from 20 to 200 km2 (7.7 to 77.2 sq mi). In San Diego County in California, the home ranges varied from 49 to 137 km2 (19 to 53 sq mi), with an average of 93 km2 (36 sq mi). However, some home ranges have been much smaller, such as in southwestern Idaho where, possibly due to an abundance of jackrabbits, home ranges as small as 4.85 km2 (1.87 sq mi) are maintained. The smallest known home ranges on record for golden eagles are in the Bale Mountains of Ethiopia, where they range from 1.5 to 9 km2 (0.58 to 3.47 sq mi). 46% of undulating displays in Montana occurred shortly after the juvenile eagles left their parents range, suggesting that some residents defend and maintain territories year-round. Elsewhere it is stated that home ranges are less strictly maintained during winter but hunting grounds are basically exclusive. In Israel and Scotland, aggressive encounters peaked from winter until just before egg-laying and were less common during the nesting season. Threat displays include undulating flight and aggressive direct flapping flight with exaggerated downstrokes. Most displays by mature golden eagles (67% for males and 76% for females) occur, rather than around the nest, at the edge of their home ranges. In Western Norway, most recorded undulating flight displays occur during the pre-laying period in late winter/early spring.
Display flights seem to be triggered by the presence of other golden eagles. The use of display flights has a clear benefit in that it lessens the need for physical confrontations, which can be fatal. Usually, non-breeding birds are treated aggressively by the golden eagle maintaining their home range, normally being chased to the apparent limit of the range but with no actual physical contact. The territorial flight of the adult golden eagle is sometimes preceded or followed by intense bouts of undulating displays. The invader often responds by rolling over and presenting talons to the aggressor. Rarely, the two eagles will lock talons and tumble through the air; sometimes fall several revolutions and in some cases even tumble to the ground before releasing their grip. In some parts of the Alps, the golden eagle population has reached the saturation point in appropriate habitat and apparently violent confrontations are more common than in other parts of the range. Golden eagles may express their aggression via body language while perched, typically the adult female when confronted by an intruding eagle: the head and body are upright, feathers on head and neck are erect; the wings may be slightly spread and beak open; often accompanied by intense gaze. They then often engage in a similar posture with wings spread wide and oriented toward the threat; sometimes rocking back on tail and even flopping over onto the back with talons extended upward as defense. Such behavior may be accompanied by wing slap against the threatening intruder. When approached by an intruder, the defending eagle turns away, partially spreads tail, lowers head, and remains still; adults on the nest may lower head and “freeze” when approached by a person or a helicopter. Females in Israel displayed more than males and mostly against interspecific intruders; males apparently displayed primarily as part of courtship. Five of 7 aggressive encounters at carcasses during winter in Norway were won by females; in 15 of 21 conflicts, the younger bird dominated an older conspecific. However, obvious juvenile eagles (apparent to the adult eagles due to the amount of white on their wings and tail) are sometimes allowed to penetrate deeply into a pair’s home range and all parties commonly ignore each other. In North Dakota, it was verified that parent eagles were not aggressive towards their own young after the nesting period and some juveniles stayed on their parents territory until their 2nd spring and then left by their own accord.
Natural sources of mortality are largely reported in anecdotes. On rare occasions, golden eagles have been killed by competing predators or by hunting mammalian carnivores, including the aforementioned wolverine, snow leopard, cougar, brown bear and white-tailed eagle attacks. Most competitive attacks resulting in death probably occur at the talons of other golden eagles. Nestlings and fledglings are more likely to be killed by another predator than free-flying juveniles and adults. It has been suspected that golden eagle nests may be predated more frequently by other predators (especially birds, which are often the only other large animals that can access a golden eagle nest without the assistance of man-made climbing equipment) in areas where golden eagles are regularly disturbed at the nest by humans. Jeff Watson believed that common raven occasionally eats golden eagle eggs but only in situations where the parent eagles have abandoned their nesting attempt. However, there are no confirmed accounts of predation by other bird species on golden eagle nests. Occasionally, golden eagles may be killed by their prey in self-defense. There is an account of a golden eagle dying from the quills of a North American porcupine (Erethizon dorsatum) it had attempted to hunt. On the Isle of Rùm in Scotland, there are few cases of red deer trampling golden eagles to death, probably the result of a hind having intercepted a bird that was trying to kill a fawn. Although usually well out-matched by the predator, occasionally other large birds can put up a formidable fight against a golden eagle. An attempted capture of a great blue heron by a golden eagle resulted in the death of both birds from wounds sustained in the ensuing fight. There is at least one case in Scotland of a golden eagle dying after being “oiled” by a northern fulmar, a bird whose primary defense against predators is to disgorge an oily secretion which may inhibit the predator's ability to fly. Of natural sources of death, starvation is probably under-reported. 11 of 16 dead juvenile eagles which had hatched in Denali National Park had died of starvation. Of 36 deaths of golden eagles in Idaho, 55% were possibly attributable to natural causes, specifically 8 (26%) from unknown trauma, 3 (10%) from disease and 6 (19%) from unknown causes. Of 266 golden eagle deaths in Spain, only 6% were from unknown causes that could not directly attributed to human activities. Avian cholera caused by bacteria (Pasteurella multocida) infects eagles that eat waterfowl that have died from the disease. The protozoan Trichomonas sp. caused the deaths of 4 fledglings in a study of wild golden eagles in Idaho. Several further diseases that contribute to golden eagle deaths have been examined in Japan. A captive eagle died from two malignant tumors – one in the liver and one in the kidney.