On Friday morning I visited the newly opened Fenti Golf Course on the edge of Khartoum for some birding. There were lots of Yellow Wagtails of many different subspecies and I tried to photograph as many as possible. I tried my best to identify them, but I have little previous experience with these forms and I would welcome some comments. I posted them on my Birding Sudan blog (link below), so rather than try to upload them all here, I was hoping that you might be able to follow the link and see them there.
Thanks
Tom
Tom
The first thing you need to be aware of is that since about the 1960s subspecies have been used as little more than a convention, and are not taken very seriously by taxonomists. When mathematical methods started to be used to classify organisms objectively, it was found that members of different subspecies didn’t cluster together, suggesting that they were largely an invention of the imagination of earlier taxonomists. Genetical studies bear this out. The latest work on Yellow Wagtails suggests that they cluster into three groups: Western, North Asian and South Asian, with little difference among the subspecies within these groups.
Because of this, no changes have been made to the subspecies classification since the 1950s, when Charles Vaurie defined the 18 subspecies that have been used ever since. Most of these refer to plumage combinations that are prevalent within substantial stretches of the breeding range, but variants are common everywhere, and it is pretty futile to speculate on their origin. Typical specimens are quite useful however, especially when trying to work out the origin of birds seen in the wintering area. I describe how in
this video – the yellow wagtail bit starts at about 5 minutes in.
So far as your photos go, the first one looks to be a quite pale M.f.beema, tending towards M.f.leucocephala, and the second a typical M.f.feldegg. The third one (and probably number 8) is M.f.lutea. ‘Perconfusus’ was a name that used to be given to birds with blue heads and yellow eye stripes found in the wintering area, in the belief that they had a mysterious Asian breeding area. Later on they were dismissed as hybrids between M.f.flava and M.f.flavissima or M.f.lutea, though even this is quite speculative.
4, 5 and 8 certainly look pretty much like M.f.thunbergi. It will be interesting to see if these disappear as the winter progresses, as the wintering range of thunbergi is much further south. I would be less sure about the one in 6 and 7, however, which looks to me more like a slightly aberrant M.f.feldegg or M.f.melanogrisea. It has a whacking great beak, which is characteristic of these southern subspecies (good for catching grasshoppers), while M.f.thunbergi typically has a short, spiky bill (good for caterpillars) like the one in photo number 8.