Saturday, October 30, 2010

maybe it is a Chandeleur Gull

I've been pooh-poohing this bird for at least 4 years now as having any Kelp Gull genes, believing Greater Black-backed to be the dark-mantled parent. Yesterday (a year to the day that I last featured it in a Tiscornia blog), the bird re-appeared at Tiscornia so Tim and I walked down after a bit to get some shots. It flew back and forth a few times so these are my first decent spread wing shots.

The bird, as usual, is in wing moult, with P7-10 retained from last year, P6 growing out, and P1-5 fresh. I think no more than a couple of secondaries are moulted, and obviously it's missing some inner rectrices as well. Note that on the outer retained primaries, the white tips of the feathers are essentially worn off.

Having pulled back up the Dittman and Cardiff paper describing the Herring x Kelp gull pairings in Louisiana's offshore Chandeleur Islands, the wing pattern does turn out to be pretty good for Chandeleur gull. Here's their description feather-for-feather with my feelings on this bird:
P10: black with a large square white mirror - yes, though maybe I wouldn't describe this bird's mirror as large
P9,8: black outer web and somewhat paler inner web - yes
P7: black outer web extending nearly to the base - yes
P6: black outer web extending partially up the feather, with the inner web dark gray and with a black subterminal band with a white tip - all those features present but this bird has a white pearl/crescent proximal to the subterminal band in addition
P5: dark gray with a black subterminal spot/bar, with a proximal white crescent above on the inner web and a large white tip - yes almost exactly, though a tiny amount of white in the pearl/crescent area is on the outer web too
P4-1: dark gray with a large white tip - this bird also has a small black subterminal band on the outer web of P4 and P3
Our bird has a little more white where Slaty-back has its "string of pearls" with some extra white on P6 and P5 for their description of a classic F1 Chandeleur gull, but overall that's pretty close, and a little more black spotting in P3 and P4, though Herrings certainly can be somewhat variable in how many of those feathers have black spotting too.
The 2nd flight shot does show the grey/green/yellow leg color which I still say sometimes looks pinkish in the webs in some lighting though Tim says I'm crazy (or need new glasses). Or both.
One of my biggest concerns about this bird in the past is that it does seem a little bigger than most Herring gulls, though in some of my pics it seems like it's longer but maybe leaner too. Since Kelp Gulls are smaller than Herring's I thought that would be a bit of a deal breaker, but perhaps not. Dittman and Cardiff say that Chandeleur gulls look about the same size as Herring gulls which the pics perhaps suggest.
Here's another of Tim's pics showing the size comparison as well.
So I guess the bottom line is that perhaps I am coming around to think of this as a Chandeleur Gull.

Just in case flight shots of black and white wings are giving you headaches, these Snow Buntings that swirled around us yesterday as well may be a bit of a relief on the eyes.

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