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Wednesday, September 28, 2011

Sandpiper fun

So I received a call and the following screen captures from Randy last night, who was at Millenium Park looking at a sandpiper he thought might be a Sanderling. But he was not sure whether it couldn't be a Semipalmated Sandpiper, and asked to me help him work through the ID before announcing the bird to anyone (good gut instinct, man!). (Sidenote: Sanderling is a much-sought-after county tick for all of us Kent Co. listers as they don't often land away from the Great Lakes shores.)
My gut reaction when seeing these was that it was probably a Semi, but I had enough doubt given the strongly contrasting face pattern, attenuated look to the rear end, and the suggestion that the bill shape was being skewed to look skinny by some photographic artifact (both SAND and SESA have relatively blunt-tipped beaks so the photo couldn't be taken at face value), that I decided to check it out. Plus I received opinions from 2 birders that they felt the bird was probably a SAND based on what they saw in the photos. I did not find the bird at dusk last night, but did have it at the same location this morning at about 7:45AM. Upon my first scope view in the rainy, gloomy weather, I felt it looked like a pretty clearcut Sanderling, based primarily on the overall black and white patterning, frosty upperparts, and overall shape and jizz. So I made the phone calls to let everyone know (woops). But quickly upon getting better looks after the rain subsided and the light came up, I was troubled by the bird's size (too small) and the lack of an obvious wingstripe. So I checked the primary projection (primaries beyond tail substantially in SAND, even with tail in SESA) and the bird clearly showed a long projection, at least 1/4 to 1/2 inch, probably on the longer end of that range, as evidenced by these 2 photos:
This primary projection was apparent at all angles, and was symmetrical. I realized that some Semipalmateds (apparently females) do show a slight projection here, but this was so substantial that I felt it strongly favored Sanderling. Here is an example of the primary projection I am used to on normal SESAs. The Millenium Park bird has more projection than I've seen on SESA personally. But again, several things seemed at odds with this putative ID: the bird's upperparts seemed strange as SAND typically shows strong spotting along the mantle fringes, not just a pale fringe as in SESA. And a final nail in the coffin for SAND was that the bird clearly displayed hind toes (!), something which took me a while to document clearly:A final mark I wanted to check out was the wingstripe, which thanks to my new DSLR setup I was able to capture as it took flight. I guess the stripe looks pretty typical for a SESA, confirming my suspicion that the wingstripe was too dull for SAND.At this point I made all of the phone calls again (in reverse order) to recant my ID. All in all the bird seems OK for a juvenile SESA, though on the dark/contrasty side, and with longer primaries (both beyond the tertials and beyond the tail tip) than any other SESA I've personally seen. I do not know if this is in the normal variation for the species (if so I need to expand my definition) or whether some additional explanation would be necessary (extra primary? [something known from godwits in the literature], hybridism, etc.). This bird, if a pure SESA, would extend the Kent Co. eBird bar chart a week father into the fall than it currently goes. Apologies to Randy who has had yet another self-found county tick squandered away (ROGO being the other): keep trying man, one of them will stick! A final parting shot:

1 comment:

Liver of this Life said...

Caleb, nice post. It goes to show you how grainy photos can mess things up. When I saw Randy's captures, I thought it looked much more like a Sanderling than when I saw your photos. Thanks for the blog post.
Jon Vande Kopple