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Re: Wagtail comments by Sibley



Hi,

It looks I am the most familiar with White  and Pied Wagtails (Motacilla alba
alba and yarrelli) and would like to make some comments.
First of all it is juvenile bird. Yellowish tinge to the "face" and throat,
grayish forehead and all wings feather in the same age indicate juvenile in
first winter plumage.  Adult would have rather pure white throat and forehead
(with only a trace of yellowish tinge on ear coverts if any) and at least some
visible moult in wings or two age type wings coverts or tertials.
The nice "open face" character of the Falls Lake bird, light loral and eye
stripe are characters for european forms (alba and yarrelli). Sometimes White
Wagtails juveniles show thin darker eye stripe but the lore is still light.
However on some photographs of White Wagtail from Japan these areas are almost
pure white in adult birds and not so distinct dark in immature. So lack of dark
line from the base of the bill toward the nape could  not ba always the only
feature to exclude Siberian form of White Wagtail. Nevertheless it looks like
both Siberian White and Black-backed have rather distinct white edges to the
greater coverts and mostly white median coverts. In "our bird" both coverts have
narrow pale grayish fringes (do not form distinct, white wing bars)
characteristic for European birds.
So now lets try to do risky business and find out is it alba (White) or yarrelli
(Pied).
The Pied Wagtail (yarrelli) in first winter plumage is superficially similar to
White one. However there is a tendency in Pied Wagtail to have more dark gray
(or blackish gray) cap and slightly darker back. In our bird the cap is gray and
there is just a hint of black right above the supercilium which is
characteristic for winter plumage of White Wagtails. However the most important
is the rump color. White Wagtail has gray rump with black uppertail coverts
whereas Pied Wagtail has  black both, the uppertail coverts and the rump. On the
photographs of the Falls Lake bird you can see the rump is actually gray (second
and the third photos from down) with more black uppertail coverts. So we are
dealing with juvenile European White Wagtail Motacilla alba alba.
Nevertheless if you will look at these photographs (nice shots by the way Will)
you should have Birds of Europe by Mullarney, Svensson, Zetterstrom and Grant
and the best book about that group of birds - Pipits and Wagtails by Alstrom and
Mild. Without the latest book any analyze of mystery wagtail would be
uncompleted. I do not have that book yet (instead I spent some time discussing
with Per Alstrom some cases of Pipits ID).
At the and I have to say I would be very, very appreciate if you found some nice
Black or Siberian White Wagtail instead of the bird I have seen in tens of
thousands! Well, next time.

Mike


Will Cook wrote:

> Here are some comments from David Sibley on the wagtail, forwarded with
> permission.
>
> ------- Forwarded message follows -------
>
> I was very interested to look at the wagtail photos you posted from NC,
> since the separation of White and Black-backed can be very tricky and both
> species have been recorded in eastern North America. I was shocked, however,
> to see that the NC bird has no dark eyeline, which excludes both Black-
> backed and the Siberian form of White Wagtail. As far as I know this bird is
> a first documented *North American* record of any of the "white-faced"
> subspecies of White Wagtail! The most likely is the European subspecies M.
> a. alba which nests as far north and west as Iceland, but I don't know
> enough to rule out the British form (Pied Wagtail, subspecies M. a.
> yarellii) or to know if there are other subspecies farther afield that could
> be confused. No matter what it is a first for North America.
>
> Congratulations! A very exciting record and nice photos.
> David Sibley
>
> ------- End of forwarded message -------
>
> --
> Charles W. "Will" Cook                  w 919-660-7423
> http://www.duke.edu/~cwcook            cwcook@duke.edu
> Biology Dept., Duke Univ., Box 90340, Durham, NC 27708

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Michal Skakuj  Ph.D.
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