Lame Byrds pun aside . . .
Forster’s Tern Nation in Alameda – Sterna forsteri
Their gravelly call precedes them, these Forster’s Terns (Sterna forsteri) with their fuzzy black berets and orange feet. They sound like aerial barflys with too much whiskey and smoke on the voice box. When it’s a row of more than 50 terns — alternately calling to each other and to the gulls that regularly interrupt their conga line — it’s some music to behold.
When perusing a field guide, there’s great similarity between the Forster’s and the Common Tern. Generally, because the Common Terns migrate through the Bay Area for a brief period, what you’re seeing is most likely a Forster’s. But check the markings to understand distinctions. Here’s a USGS list of field markings for Common Terns and also the corresponding marks for Forster’s Terns.
Note, too, the variations in colors among these Forster’s. The black patch over the eye signifies an adult bird with non-breeding plumage, contrasted with the full black cap which constitutes breeding plumage. (Breeding feathers are changes, usually dramatic color shifts, which occur in bird plumage during their breeding seasons.)
There was a blissful wisp — just a wisp — of wind as we started our walk. Two hours later, with patchwork sunburns where the zinc oxide didn’t hit, we’d grabbed shots of arguing terns, flying terns, fishing terns, and out-of-focus terns. These little guys are small and fast, and dive with the velocity of a torpedo.
It’s possible to mistake terns for gulls (albeit extremely small gulls) if you don’t know terns (or gulls). Once you recognize the terns’ unique wing structure and coloration (with variations across tern species, of course) you’ll notice the choppy flying patterns as contrasted with the somewhat steady and languid wing strokes of a gull.
Forster’s Terns hover and flutter before plunging head first for marine eats just below the surface. And their flying style tends to be choppy, prone to sudden turns and changes of course — exacerbating the difficulty in photographing them well.
We were in awe, watching them maneuver this way in extremely shallow water — in dives that should have been concussive, but which ended with a bare grazing of the water’s surface, a bill full of food, and a graceful recovery — with wingtips fluttering through their reflections.
More about Forster’s Terns: All About Birds (Cornell Lab of Ornithology)