Mike et al
 
I'm not sure that this bird is a good candidate for Black-headed. Bonaparte's can have quite bright legs when in full breeding plumage, consistent with the color that can be made out (and Black-headed can have quite dark legs, and bill, early in the breeding season).  The shape of the hood depends very much on how the bird is holding its head and is best used as a field mark if you can see the bird in the field in a variety of poses.  Also it does not actually look all that much larger to me than some of the obvious Bonaparte's - possibly it looks taller because its standing on something? I would've expected a Black-headed to look like the distinctly larger bird it is, more intermediate between the Bonies and the Ring-billed than this bird appears.  Finally, the mantle looks as dark as any of the other birds, and a little darker than some of the Ring-billed, whereas you might expect Black-headed to be a little lighter than Bonaparte's when seen in overcast conditions.  Still,
 definitely worth checking again for more definitive views.
 
Regards
 
Clive Harris
Cabin John, MD

Michael Bowen <> wrote:
I looked at June's pictures, and agree with Bob Ringler that the bird in 
full alternate plumage on the right of Photo #5 is probably a 
Black-headed. While it's not possible to see subtleties of color 
(Black-headed's hood is dark chocolate brown rather than black), I am 
struck by how red that bird's legs look in a photo where you can hardly 
make out the color of the other birds' legs. Adult Black-headeds show 
brighter crimson-red legs than the more subdued orange-red of 
Bonaparte's. And as Bob notes, the way the hood does not extend down the 
hind neck is more typical of Black-headed.

The photos of the gulls in flight do not provide much help, unfortunately, 
or it might be possible to see the longer wings of Black-headed and/or the 
distinctly dark areas on the underside of the primaries.

Mike Bowen
Bethesda, MD



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