They're Dunlin. Except if they look nearly white and/or are chasing waves on the beach - then they are Sanderlings. Or if they're taller, upright, and plump - then they're Black-bellied Plovers. See, you too can be a winter shorebird expert. . .
O.k., so maybe it's not quite that simple, but December-February, if I see a flock of shorebirds flying over a mudflat I'll confidently call them Dunlin at any distance. Unless they're whitish and/or over a sandy beach, in which case they are Sanderlings.
Red Knot, Western Sandpiper, and the odd wintering yellowlegs, Semipalmated Plover or Least Sandpiper complicate the winter shorebird department, as do Purple Sandpipers and Ruddy Turnstones (almost always on rocks); Marbled Godwit; "Western" Willet (very tall, pale, flashy wing pattern); and of late, returning Piping Plovers, the first of which was detected at Two Mile Beach by Tom Reed. I also understand Sam Galick wins the LAGU award for the first of season Laughing Gull he saw at St. Peters yesterday.
[American Oystercatchers are shorebirds (the biggest ones we have) and can be found in small numbers in winter, but hardly complicate things, flying around blowing their whistles like Keystone Cops smoking orange cigars. . . these obey the traffic signal on the free bridge to Nummy Island, February 23, 2011.]