Blue-footed Booby (Sula nebouxii) 19 September 2013 Seal Rocks, Cliff House, San Francisco, CA Photos © 2013 Joseph Morlan








High resolution images of the spread wings to show molt. Steve Howell commented, "The images are not high enough res to be completely sure, but it looks like p1 is new on both wings, and the rest of the pp are juv (the inners look fresher than the outers because they are more protected relative to the exposed and more pointed/worn outers); also, the ss look uniform juv and if 2 waves of p molt had started the ss would not be uniform juv. Tail looks like a trashed juv tail (uniform generation rects), perhaps because the bird was fed poor food, which might be linked to to northward invasion."

Peter Pyle agreed writing, "I agree that it has begun a molt, with p1 growing or new, as best seen in image 497 but ascertainable of both wings in all images. The left central rectrix (r1) has also been replaced, as possibly have several wing coverts, and one or more tertials may also have dropped. This would all make sense for a bird beginning the second prebasic molt, and would indicate a bird of 8 months of age according to the literature. If so it may have hatched in January or February, and for a booby subject to so much solar exposure, this easily explains the wear on the rectrices and other flight feathers. I see what you mean about the s3 but since this does not show up in any of the other images or the right wing, I think it's an artifact of the image. The first secondary besides tertials to drop in boobies (and most large birds) is usually s5 (occasionally s1) and this feather looks the same as the others. The substantial uniformity of the flight feathers otherwise still convinces me that this bird is an HY just beginning the PB2. I've linked a couple of older flying BFBOs that I found on line, for comparison of flight feathers."

More details here.

Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).

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