Monday, September 7, 2009

Quiz #316 (2009-3-11) Answer

Click the picture for a larger view.

Only the flying birds need be identified.

Answer by Tony Leukering

Only the flying birds need be identified.

That was the caveat provided for this week's quiz photo and many probably breathed a sigh of relief. That is because all of the flying birds are in the focal plane of the picture and in front and no one had to deal with the out-of-focus gulls in the background. A couple respondents noted that though they couldn't find a third species, they were concerned that there was a possibility that they had missed such.

When I posted this quiz photo, I posted it with that very thought in mind: give our players a lot of birds to pick through with absolutely nothing hidden. I checked all of the responses and started writing the solution with reference to the picture when I noted something else. There is a hidden species!

The lovely Ruddy Turnstones are obvious and virtually all the other birds are a bewildering variety of Sanderlings, with their wide, white wing stripes, but with birds in full alternate plumage, birds in full basic plumage, and others in between. Yes, there are individuals that might seem smaller, but all of those ('cept one) either sport the Sanderling wing stripe or have so little of the bird visible as to be unidentifiable.

However, just left of center and below center, to the left of the nearly-overlapping Ruddy Turnstones, there is a peep. It can be told by its stronger face pattern, particularly it's strong superciliary, and its thin wing stripe. I provide here a enlarged version of that part of the picture with the bottom-left arrow pointing up to the bird, the middle arrow pointing at the thin wing stripe, and the right arrow pointing at a typical Sanderling wing stripe.

Now, though, we have to ID the bird and that's not all that easy (and I apologize for the difficulty that I hadn't intended). We can quickly rule out Least Sandpiper, as the bird's wingtip is quite pointed, not the somewhat-rounded wingtip of Least. That species is also eliminated by the underparts pattern, as the bird doesn't show a distinct hood. Long-toed Stint is similar in these regards. The small size and, to some extent, the head and chest pattern, rules out the larger White-rumped and Baird's sandpipers, leaving us with Semipalmated and Western sandpipers and Little and Red-necked Stints. The two stints are ruled out simply on the bill length.

Separating Semipalmated from Western given this view is close to impossible, though some features point toward Semi and few do to Western. Given that the picture was taken in spring in New Jersey, Semi is the odds-on favorite given that Western is fairly rare in spring there. Unfortunately, I took the picture in Villas, Cape May Co., NJ, on 1 June 2009 and what spring Westerns show up there often show up in very late spring. I spoke with Cameron Cox (see his article on peeps in Birding) and he agreed with me about the ID as Semipalmated based on the "dirtiness," thin wing stripe, and strong facial pattern.

As late-season peeps tend to be females, the bird's long bill is not the deal-breaker for an ID of Semi that some might have thought -- it is within the range of variation of the species. However, Cameron also agreed that the bird is probably not definitively identified. Thus, my solution to the problem is to accept as correct identifications of that bird as either Semipalmated Sandpiper, Western Sandpiper, or unidentified, which has the happy consequence of making the vast majority of responses correct! However, I will give the extra bonus point of another correctly identified species each to George Cresswell and Bryan Guarente, the only two respondents that provided answers with Western and Semipalmated sandpipers, respectively, and without any other incorrect species.

Both incorrect respondents provided both correct species, but their answers presented too many species.

Incorrect species provided as answers:
Herring Gull - 1
Great Black-backed Gull - 1
Western Sandpiper - 2
Least Sandpiper - 1
Purple Sandpiper - 1
Dunlin - 1

The 14 of 16 providing the correct answer:
Al Guarente
Ira Sanders
Tammy Sanders
Nick Komar
Mark Dettling
Robert McNab
Kevin Kerr
Su Snyder
George Cresswell
Aaron Brees
Margie Joy
Peter Wilkinson
Tyler Bell
Bryan Guarente

Answer: Ruddy Turnstone, Sanderling, and Semipalmated/Western Sandpiper