Western Sandpiper or ?

[Cin-Ty]

Hi everyone,
I was forwarded this photograph by Monte and Christopher Taylor. It's a sandpiper photographed in Georgia (USA) in January 2008. Western Sandpiper is the default winterer in North America, but this bird has a very short bill. Is it a Semipalmated Sandpiper? Wintering Semipalmateds are very rare here. Bill is very short, but somehow the shape of the bill doesn't quite match for Semipalm for me and the overall shape of the bird also doesn't match Semipalm. Is this just an unusually short-billed male Western?
cin-ty

[AndyB]

Hi Cin-Ty, good one. I've been looking out for these really small-billed male Westerns for years (whilst searching for vagrant Semips in CA) and not had much luck or not at least as short as this bird. If I was scanning through a flock, bill size alone would call for attention but I think this could be a useful example of using jizz to help with the ID. I'd agree that strucurally, there a lot of pro Western features. Lars Jonsson's Birds of Europe mentions the center of gravity being further forward with Western and it's a pretty good tip. They often look like they are about to tip over. Also, note the tapered rear compared to Semipalmated.

However, my experience is much more limited than the east coast birders on here so would like to hear their opinions. It's got a very short bill so wouldn't be surprised if I'm completely wrong with the theory here:

Pros
Bill length definitely within range for Semip - see here (http://amykane.typepad.com/photos/uncategorized/2007/05/15/800pxcalidrispusilla001.jpg).

Cons
* Look at center of gravity and compare to this Semip in a similar pose (http://www.scillybirding.co.uk/images/Semi-palmated_Sandpiper_St._Agnes_04-09-06_Bryan_Thomas.JPG)
* Rear of bird tapers and sweeps upwards. Compare to this Semip (http://www.birdinfo.com/A_Images_S/SemipalmatedSandpiper2005-09-12-001stint.jpg) - here's also a slim Semip (http://amykane.typepad.com/photos/uncategorized/2007/05/15/800pxcalidrispusilla001.jpg) with a tapering rear but still note shape compared to Western.

Attaching a silhouette chart showing rear of Western vs Semip on classic birds (which we may not be dealing with here). On the powerpoint, the red ball rolls down the back in case you're wondering what that is!

[coeligena]

For what it's worth, I also agree with Andy. The bird just looks very front-heavy (as if the legs were somehow set too far back) and to me that is very reminiscent of Western. It looks pretty large-headed as well, which I would think is another point in favor of Western. I don't know what to say about bill lenght, I don't know that I've seen a Western with such a short bill before but I guess there is enough variation in bill lenght that an extreme bird might look like that.

[Sean Cole]

From memory and without reference to books I think the breast-side streaking on this bird indicates Wetsern - it is confined to discreet patchs on the side, with fine streaks. On Semip it is more extensive and almost meets in the middle.

Western for me.