Sanderlings in Molt

This past August I spent a few days birding Long Island getting my shorebird fix for the year (yes, I am just now putting something together to post). One of the best reasons to visit the Long Island beaches is to see the big flocks of Sanderling playing in the waves.


When taking big flock shots of birds, I like to zoom in afterwards and look for things I missed. When I took a look at the big Sanderling flock, I noticed a large number of birds in primary molt. I thought it unusual for a migrating flock of shorebirds to be molting flight feathers on a staging ground. Upon review of The Shorebird Guide and the Sanderling Birds of North America account, it seems this is not unusual at all. Adult Sanderling should be undergoing a complete prebasic molt into non-breeding plumage, replacing all of their flight feathers in late summer and early fall. Since the staging areas along the Long Island coast are also wintering areas for at least some Sanderling, they are not necessarily even going anywhere. In contrast to the adults, juvenile birds undergoing molt into their first, incomplete, basic plumage retain their juvenile flight feathers and should not be showing this condition in August. So, this neat little factoid I noticed after the fact is actually a roundabout way of aging Sanderling. Fancy that.