Friday, May 14, 2010

OK I lied.

May isn't for warblers. It's for looking for good birds. Like this Franklin's Gull, on the beach for a bit at Tiscornia this morning. Some sub-adult Franklin's Gulls can be hard to separate from Laughing Gulls; the classic Franklin's half hood with big eye arcs makes this one pretty easy.
Note the Forster's and Common Tern behind it; they're not always this easy to separate from each other either.

The assumption looking at the bird at rest would be that it's not a full adult since a full adult should have a full hood. In flight we can see a couple black feathers in the wing coverts, indicating retained immature feathers for this 1st summer bird.
If this bird had a more confusing head pattern it would be harder to separate from Laughing Gull. The flight pattern would still be helpful though. In flight we see that the white trailing edge of the wing bleeds into the primaries such that the black primary tips are somewhat separated from the gray of the rest of the wing.
The underwing also shows extensive white at the bases of the primaries.

Here's another view of the underwing. Of interest is that P10, the outer-most primary, is a retained feather from last fall, with the black (which extends the length of the feather) faded paler than the black of the feathers new this spring (note that Franklin's is the only gull to moult flight feathers in spring and fall).
As a comparison here's a montage of one of the Laughing Gulls from the other day.
Here's hoping that cooperative passerines on Birdathon make me eat my words again...




1 comment: