New Terns

Caspian Terns (Hydroprogne caspia)

From a distance with the naked eye I thought they were gulls. But as soon as I got the zoom lens on them, it was obvious that the only thing they had in common with gulls was the size. I had never seen these before. My guess in the field was that they were Elegant Terns, but once I got the images home and up on the big screen, that didn’t fly. Elegant Terns have longer, more delicate bills, slightly downcurved, and shaded yellowish, and they’re a slender bird. Merlin, the online bird ID app from Cornell, nailed them: Caspian Terns. The hefty, straight, reddish bill, plus the black feet, plus the broad beam and size, left no doubt. So, I’m happy to add this discovery to the Chavez Park Bird List.

Caspian Terns are named after the Caspian Sea. I looked it up and learned that it’s the largest lake in the world. It does not drain into an ocean. It contains about 3.5 times as much water as all the North American Great Lakes put together. It was until recent times (read, until modern petroleum extraction) a vast bird breeding ground, and still today contains large legally protected rookeries on the Tyuleniy Archipelago. However, today’s Caspian Terns breed in geographic patches all over the temperate world, including around our Bay Area.

What this pair was doing here in the midst of mud exposed by our record minus 2.1 ebb tide, I could not tell. At first there was only one. Then the second one flew in, stayed near and casually interacted with the first, and then flew off by itself. Neither of them made any effort to hunt or to forage. I eventually walked away, leaving the first tern still in place. It had moved only a few ungainly steps from its initial position. They are powerful fliers. They hunt fish by plunge-diving, same as other terns, except bigger.

More about them: Wikipedia Cornell Audubon

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