Eastern Yellow Wagtail
I have pondered whether to upload this photograph as the quality isn't great but I felt there was quite a lot of interesting things to say about it. I know there are much better photographs of this bird but in my defence it happened to be a dull, wet day when I had the opportunity to photograph it. It was found near Sedgeford, Norfolk on 23 December and was seen daily until 1st March, and I saw it on 23 February when I was due to be in Norfolk anyway.
Until recently Yellow Wagtail was thought to be a single species with numerous, highly variable races ranging right across the Palearctic zone and even across the Bering Strait into Alaska. But most of the plumage variability was in Europe where birds with black, grey, blue and yellow heads occurred. Across Siberia the variation seems to be less noticeable. The calls were variable too but those in eastern Siberia east of Lake Baikal had consistently more buzzing calls, similar to Citrine Wagtail. But confusingly, these buzzing birds appeared to be identical to birds breeding in adjacent areas to the west that gave more typical Yellow Wagtail calls. Don't forget Yellow Wagtails are highly variable and can have heads ranging from black through grey, to blue and yellow. So if eastern and western birds were different species it would be a remarkable coincidence for them to have evolved an identical plumage in the areas where they come together. But that is exactly what appears to have happened as the area where they meet has western Yellow Wagtails of subspecies thunbergi next to eastern Yellow Wagtails of subspecies plexa, which are inseparable on plumage. Although juveniles of eastern birds appear to be very grey and white, lacking brown or yellow tones like western birds. It was also noticed that they inhabited different habitats, with buzzing Siberian birds nesting on peat bogs whereas the sweeter calling birds were nesting in grasslands. The only morphological difference was that eastern bog breeding birds were found to have a slightly longer hindclaw than western birds. When their DNA was analysed it was found that the eastern buzzing birds were remarkably distinct genetically in both nuclear and mitochondrial DNA. And this difference is much, much greater than the difference between say black-headed and British yellow-headed Yellow Wagtails, which look remarkably different. So the Yellow Wagtail has now been split into two species; the Western Yellow Wagtail (Motacilla flava- which breeds in Europe including Britain, and Siberia west of Lake Baikal), and Eastern Yellow Wagtail (Motacilla tschutschensis- which breeds in eastern Siberia and Alaska). The Eastern species has four subspecies (tschutschensis, plexa, taivana and macronyx) and winters in SE Asia, Indonesia and northern Australia but remarkably a small number have been found to be wintering in Britain. Any Yellow Wagtail in Britain in winter is unusual as European breeding birds migrate to sub-Saharan Africa.
This adult Eastern Yellow Wagtail that has spent the winter in Norfolk is of the nominate subspecies tschutschensis, which remarkably coincided with a juvenile in Northumberland. This adult that I photographed was frequenting a dung heap in a large arable field and was frequently giving its harsh, buzzing call, that sounded dissimilar to Western Yellow Wagtail. Bizarrely this subspecies is known as Alaskan Yellow Wagtail, because it does breed in Alaska, but the bulk of the population of this subspecies breeds in Northeast Siberia (Chukhotka). And incidentally the scientific name tschutschensis is a latinised version of the Chukhotski Peninsula in eastern Siberia, which is the type locality from which the eastern species was first described in 1789 by Johann Gmelin, though at that time it was considered a subspecies of Yellow Wagtail.
Eastern Yellow Wagtail
I have pondered whether to upload this photograph as the quality isn't great but I felt there was quite a lot of interesting things to say about it. I know there are much better photographs of this bird but in my defence it happened to be a dull, wet day when I had the opportunity to photograph it. It was found near Sedgeford, Norfolk on 23 December and was seen daily until 1st March, and I saw it on 23 February when I was due to be in Norfolk anyway.
Until recently Yellow Wagtail was thought to be a single species with numerous, highly variable races ranging right across the Palearctic zone and even across the Bering Strait into Alaska. But most of the plumage variability was in Europe where birds with black, grey, blue and yellow heads occurred. Across Siberia the variation seems to be less noticeable. The calls were variable too but those in eastern Siberia east of Lake Baikal had consistently more buzzing calls, similar to Citrine Wagtail. But confusingly, these buzzing birds appeared to be identical to birds breeding in adjacent areas to the west that gave more typical Yellow Wagtail calls. Don't forget Yellow Wagtails are highly variable and can have heads ranging from black through grey, to blue and yellow. So if eastern and western birds were different species it would be a remarkable coincidence for them to have evolved an identical plumage in the areas where they come together. But that is exactly what appears to have happened as the area where they meet has western Yellow Wagtails of subspecies thunbergi next to eastern Yellow Wagtails of subspecies plexa, which are inseparable on plumage. Although juveniles of eastern birds appear to be very grey and white, lacking brown or yellow tones like western birds. It was also noticed that they inhabited different habitats, with buzzing Siberian birds nesting on peat bogs whereas the sweeter calling birds were nesting in grasslands. The only morphological difference was that eastern bog breeding birds were found to have a slightly longer hindclaw than western birds. When their DNA was analysed it was found that the eastern buzzing birds were remarkably distinct genetically in both nuclear and mitochondrial DNA. And this difference is much, much greater than the difference between say black-headed and British yellow-headed Yellow Wagtails, which look remarkably different. So the Yellow Wagtail has now been split into two species; the Western Yellow Wagtail (Motacilla flava- which breeds in Europe including Britain, and Siberia west of Lake Baikal), and Eastern Yellow Wagtail (Motacilla tschutschensis- which breeds in eastern Siberia and Alaska). The Eastern species has four subspecies (tschutschensis, plexa, taivana and macronyx) and winters in SE Asia, Indonesia and northern Australia but remarkably a small number have been found to be wintering in Britain. Any Yellow Wagtail in Britain in winter is unusual as European breeding birds migrate to sub-Saharan Africa.
This adult Eastern Yellow Wagtail that has spent the winter in Norfolk is of the nominate subspecies tschutschensis, which remarkably coincided with a juvenile in Northumberland. This adult that I photographed was frequenting a dung heap in a large arable field and was frequently giving its harsh, buzzing call, that sounded dissimilar to Western Yellow Wagtail. Bizarrely this subspecies is known as Alaskan Yellow Wagtail, because it does breed in Alaska, but the bulk of the population of this subspecies breeds in Northeast Siberia (Chukhotka). And incidentally the scientific name tschutschensis is a latinised version of the Chukhotski Peninsula in eastern Siberia, which is the type locality from which the eastern species was first described in 1789 by Johann Gmelin, though at that time it was considered a subspecies of Yellow Wagtail.