Re: Vega and possible Slaty-backed photos

Noah Arthur

I have been kindly reminded by my gulling buddy that it would be helpful if I mentioned why these birds are Vega and potentially Slaty-backed Gulls, instead of just saying they are and expecting you all to believe me!
The Vega shows more white than dark on the greater coverts, with a rather messy pattern of dark marks (rather than sharp checkering in neat rows, which is more typical of American Herring). The head is very sharply streaked. The rump and undertail coverts are extensively white, and -- best of all -- the tail has a checkered white base and solid dark terminal band. The primaries are very dark, which should rule out all hybrids involving paler species. To me, that's everything I'd like a Vega Gull to give me, so I'm confident in this ID, although I'm still open to dissent. 
The Slaty-backed is worn and more difficult, but there are some things that are pointing me to Slaty rather than any of the expected hybrids. The bill lacks a strong gonydeal angle and the tail has fairly extensive white at the base, both wrong for Glaucous-wingedXWestern. Glaucous-wingedXAmerican Herring is much harder to rule out, but this bird's very bulky shape when relaxed, as well as the stubbornly dark primaries on a very worn bird, don't seem typical of that hybrid. I know I'm wading in dark muddy water here with trying to ID 1st-cycle Slaties, however...

On Monday, March 31, 2014 10:58 AM, Jack Hayden wrote:
Nice! Could I get you to explain to me what is going on about the Vega that gives you confidence about the ID? I'd appreciate it. Cheers, Jack

On Mon, Mar 31, 2014 at 11:44 AM, Noah Arthur <semirelicta@...> wrote:
Finally got the internet going fast enough to upload pictures, so here are the photos of this month's two standout gulls from the San Leandro Marina:
Noah Arthur, Oakland

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