This ought to be easy, telling "peep" from the larger Sanderlings. And it is pretty easy if the two are side by side. But what if there's a single small sandpiper on the beach - how do you know if it's a Sanderling or a Semipalmated Sandpiper (or other "peep")?
Habitat and behavior are great clues, but before we get into them, try this exercise:
1. Flick your eyes back and forth between the bills of these two birds a few times, taking in your impression of any differences.
2. Do the same thing with the legs.
3. Do the same thing with their midsections.
This trick of looking rapidly back and forth between two birds in a picture, or separate pictures, or even in the field when possible, while focusing on a single character can really help you see differences. Here, what you should see that the bird in the foreground has a shorter, finer, and finer- tipped bill; thinner, more delicate legs (and it has a hind toe); and a slimmer midsection. That's the Semipalmated Sandpiper. The Sanderling, in back, is chunkier, thicker-legged, and sports a thicker, straighter bill.
Habitat can often separate these two, at least in one direction: if it's on mud, it's not a Sanderling. If it's on sand, it could be either. If it's on sand but really actively chasing the waves back and forth, up and down the beach slope with each wave, with legs moving so rapidly they're blurs, it's a Sanderling. If it's feeding more slowly, walking or running but stopping to probe, and often away from the waves, it's probably a Semipalmated Sandpiper (unless it's a Western Sandpiper, another story.)
There are plumage differences too, but in this photo the Sanderling in rear is in transition from breeding to nonbreeding plumage, and so is not the sandy-white bird we're familar with later in fall and in winter. In other words, though with scrutiny its pattern is clearly different than a Semi's, the difference is not as clear cut. But the shape is.
This Semipalmated Sandpiper, front, and Sanderling, rear, were photographed at Stone Harbor Point, NJ on August 4, 2012.
Sanderling foraging behavior is much more varied than implied here. Sanderling do chase waves, as you describe, but often they forage above the wave washed zone, walking slowly, running but stopping to probe, particularly if there is wrack on the beach. Semipalmated Sandpipers, in contrast, rarely if ever chase the waves back and forth (they're both Calidris, so I never say never). BTW... your photo nicely shows that while Semipalm Sandpipers have a hallux (rear toe), Sanderling do not. It's an adaptation for running fast on the beach.
ReplyDeletePete Myers
Thanks for this post. It will be very helpful for me. I'm in an environment with lots of peeps and shorebirds, so these tips will be handy for distinguishing the little guys.
ReplyDeletei was just at the beach....old silver beach in north falmouth cape cod....single bird...was going through the dilemma...sanderling or semipal sandpiper....after reading this..going with semi....also is it more common to see semi's by themselves whete sands sre more common in groups???
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