Monday, March 30, 2009
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Answer by Tony Leukering
I heard a great sigh of relief when this picture got posted on the Mr. Bill Mystery Quiz, as it was of a single, well-depicted bird. It's definitely a new quarter! But, of course, there's always a catch. We don't have four species of gulls to ID, but the quiz bird is a shorebird. And a drab one at that. And it has no legs!
First, let's get the bird into a general group of shorebirds. The bill rules out all of the plovers and that and the plumage rule out all of the 'odd' shorebirds (e.g., oystercatchers and avocets) at the front of shorebird taxonomy. Also, unless our quiz bird is standing in a really deep hole, our bird does not belong to one of the long-legged sandpiper genera (e.g., Limosa or Limnodromus), thus our bird is probably of that well-loved genus, Calidris. Additionally, the compactness of the bird and the not-really-overly-long bill suggest that it is one of the peeps, that group of small sandpipers that make many a birder's knees quiver.
Second, we need to age the beastie, as one should do for most shorebirds preparatory to IDing them. The bird seems to have no distinctive feathers, either bright-edged juvenal feathers or dark-centered adult alternate-plumage feathers. This makes things a bit sticky, as the bird is, thus, in basic plumage and could be of any age. Yes, the vast majority of young-of-the-year peeps retain at least a few juvenal feathers (usually scapulars or coverts) that allow for ageing, but some do not. So, we'll forego ageing for the nonce.
Assuming that our assumption about the bird being a peep is correct, let's try to whittle down the options -- there are currently nine peep options on the ABA list. Looking at our bird's wingtips, we can see that they fall short of the tail tip, and that by a fairly large margin. This, then rules out the two large, long-winged species: Baird's and White-rumped. The upperparts coloration can also help us, and the very grayish-brown look is quite different from the rich and warm brown of both Least Sandpiper and Long-toed Stint. In fact, those warm-brown species also both show more of a hooded effect with brown extending down through the throat and chest, features inconsistent with our bird. So, that's four species gone and four more to eliminate. Temminck's Stint is the odd-man-out of the remaining options, but that species, like Least and Long-toed, is a brown, hooded peep.
While it's good to have ruled out five of the nine options, that elimination does leave us with the stickiest set of four species: Semipalmated and Western sandpipers and Little and Red-necked stints. Even given good photographs, some individuals of these species are not definitively identifiable. However, we are 'blessed' with a bird with quite a long bill, and that should help us out quite a bit. The two stints still remaining under consideration do not sport such long bills, so we're left with the all-too-common conundrum of Semi vs. Western.
Our bird, unfortunately, is not foraging, so we lose some of the features that might help us ID the bird (e.g., water depth). However, a recent article on peep ID by Cameron Cox in Birding magazine (http://www.aba.org/birding/v40n4p32.pdf) makes some suggestions that are quite useful. Our bird has a substantial chest and a head that is longer than deep, both features suggesting Western Sandpiper as the ID of our mystery bird. Combine that with the long bill that tapers to a fine point and droops ever so slightly, and our initial ID firms up quite nicely. As a final minor point, note the slightly rufescent cast to the auriculars, a feature usually more noticeable on Western than on Semipalmated.
I took this picture of a basic-plumaged Western Sandpiper (probably an adult) at Stone Harbor Point, Cape May Co., NJ, on 23 September 2005, the same date on which I took the photograph that was used as Mr. Bill Mystery Quiz #168 (http://cfo-link.org/MrBill/answer.php?quiz_number=168) and which you will find in the aforementioned peep-ID paper.
Tallies of incorrect species provided in answers:
Sanderling - 1
Dunlin - 2
Semipalmated Sandpiper - 4
The 27 of 33 providing the correct answer:
Answer: Western Sandpiper