[Birdtalk] Re: [Birdnet] Plover photo

[Mark Stackhouse]

O.K., I think I'm ready to wade into this one (not too shy about it, 
but wanted to do a little review of the literature first). First, Cliff 
is right, it's definitely an adult bird - the black remaining on the 
belly means it's been through at least one breeding season. This is 
perhaps unfortunate, as the i.d. might be a bit easier if it were a 
juvenile.

As far as what type of plover, I think we can safely say it's not a 
Black-bellied, due to the small, thin bill and overall brightness of 
the plumage (remember that it's an adult, and all adult Black-bellied 
Plovers would be much grayer).

Now, which of the Golden-Plovers? My first impression was American (and 
I don't think that it was just because that would be more likely). Most 
of what I can see, and was able to confirm in my "literature review" 
seems to support this first impression.

The nature of the photograph makes this i.d. even more challenging. 
Some of the conventional field marks, wing-tail length, primary 
extension and number of exposed primary tips cannot be seen well enough 
in this picture. Also, the bright lighting makes it a bit hard to judge 
subtle colors, such as how yellow/gold the spots on the back appear. 
The angle and posture of the bird makes judging the overall length, 
uprightness of the stance and leg length (all things I've used to pick 
likely Pacifics out of flocks) difficult.

So what does this leave us? Not much, but maybe just enough.

First, there are a couple of structural features which we can see (I 
always like thing that are independent of plumage/lighting). The bill 
seems very thin and short - both good for American, as most Pacifics 
have a somewhat thicker, and especially longer, bill. Also, Pacifics 
usually look somewhat larger headed, and this bird's head looks rather 
small. Nothing definitive in this, but suggestive.

The plumage characters are complicated by the fact that the bird is 
still molting. However, both Golden-Plovers start molting the head and 
facial feathers quite early, sometimes even while still incubating, so 
the head of this bird is probably fully in basic (non-breeding) 
plumage. There are several plumage characters on the head that can be 
useful, and they all suggest American in this individual. First, the 
supercillium is very white (usually a bit buffier in winter Pacific), 
and, more importantly, is wider past the eye and continues towards the 
nape rather than sharply bending down and around the auriculars. The 
effect of this is to make the dark stripe from the crown down the nape 
very narrow, whereas on the Pacific the dark patch on the nape is 
wider. This field mark is well illustrated and described in the new 
shorebirds guide by Michael O'Brien, et. al. Also on the head, the 
"loral smudge" in front of the eye and the auriculars behind the eye 
both look quite dark (though this might partly be because the face is 
in shadow), which is better for American.

Another good plumage feature in basic-plumaged Golden-Plovers is the 
brightness of the back, probably due to larger yellow spots on the 
Pacific, though they may be yellower in some individuals as well. 
Regardless, Pacifics usually look brighter/yellower than Americans. 
This is hard to judge on the bird in the photo because of the partial 
molt and the harsh lighting. However, the new feathers that have come 
in look to me to be rather dull and unspotted - which again suggests 
American.

Perhaps the strongest evidence that this is an American has to do with 
the molt sequence and timing. In general, the Pacific completes its 
pre-basic molt a little sooner than American, and the sequencing of 
parts of the body is slightly different. In particular, Pacific 
Golden-Plovers molt their underparts before their back, so that in many 
individuals in September the belly is fully white while the back 
retains breeding plumage until October. This bird is molting both the 
back and the belly at the same time, as in American.

It's not as clean an I.d. as most of us would like (including me), but 
I'm sticking with my first impression that this is an American 
Golden-Plover.

Good birding!

Mark Stackhouse
mark at westwings.com
801-487-9453 (Salt Lake City, Utah, USA)
011-52-323-285-1243 (San Blas, Nayarit, Mexico)

On Aug 30, 2006, at 4:25 PM, Utah Birds wrote:

>
> The Plover photo taken at the Antelope Island Causeway by Keith Evans 
> and submitted by Kris Purdy has been posted on the Hotline Photo page 
> at the following address:
>
> http://utahbirds.org/hotlinephotos/index.html
>
>
>
>
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