Posted by Matthew Kenne (65.219.76.158) on August 11, 2002 at 15:52:37:
Wow, what an excellent puzzle- the only thing I'm sure about here is this ain't no hendersoni dowitcher! OK, moving on from the discussion about the dowitchers last June, the curvature of the bill is maybe a good mark for Long-billed, and the primary projection is maybe a good mark for Short-billed. Phil Pickering proposed a possible difference in the barring pattern of tertials and scaps between the two species, but, without actually seeing this drawn out before me, I'm not sure where this bird falls in the scheme of things.
The molt schedule is another clue that is garbled to me. I'm assuming San Diego is a normal wintering area for both dowitchers, so Short-billed could/should be in the middle of molting to basic plumage (according to Dunn's statements), and Long-billed could/should have completed its molt before arrival. Point for Short-billed. I turned to Shorebirds of the Pacific Northwest, by Dennis Paulson, for fall molt help and found these conflicting statements: under Short-billed- "Adults begin body molt soon after arrival, underparts showing more and more white and then upperparts more and more gray. In northern part of region body molt essentially complete in some individulas by mid August." But under Long-billed: "Adult Long-billed may molt more rapidly than Short-billed in fall and typically look gray-headed (more so than Short-billed) while passing through the Northwest. Molt into non-breeding plumage begins in late August, and by late September many adult Long-billed in virtually complete nonbreeding plumage." How can Paulson's description of body molt in non-wintering areas be so opposed to Dunn's? If this molt-timing argument is limited to primary flight feathers, with LB in active molt on migration while SB isn't, we're up the creek with this photo.
But I'm sure it's a dowitcher.