Tweeters: Just thought I'd throw in a few cents worth on the Slaty-backed vs vegae vs Western Gull discussion. I'm with Mike, the one Slaty-backed is a slam-dunk but the other two Brady Loop birds (based on the photos) could just be pale-eyed Westerns. Still, further study might reveal them to be such, if the other vital details are collected (my apologies if someone already had those and I missed it). The first bird of the two "maybe" birds is very similar to a bird I found at Graysmarsh a few years ago, also in mid-March; closer study revealed primary detail from below and other features that eliminated Western. One problem is that existing literature to date has been weak on 3rd cycle/winter SB Gull, although the recent Howell/Dunn guide to Gulls of the Americas provides alot of new data, and internet sweeps can generate a lot of photos from Japan.
In Petropavlovsk-Kamchatskii, and elsewhere on the Kamchatka Peninsula, Slaty-backed was overwhelmingly abundant when I spent much time there in the 90s--about like GW and GW x Western here. Indeed, it was outnumbered only by Black-headed Gull in late summer/early fall. Looks at thousands of Slaty-backeds there led me to believe the following: 1. Mantle color showed some variation in adults and 3rd cycle. It is not impossible that hydridization with either vegae or GW Gulls may have been involved, but at least til now this seems somewhat conjectural as to extent, notwithstanding that Howell/Dunn cite zones of breeding range overlap with vegae (near the ne Kamchatka coast), and with Glaucous-w (in the Komandorskiye Islands). I'm going to make contact with some old friends in Kamchatka to ask if anything new has been learned to date on this score as far as zones of hybridization with other taxa. Variation aside, 3rd cycle birds often do seem to be a bit paler on the mantle than adults. And then some observers have noted correctly that angle to sun, amount of glare and other lighting issues can certainly create subtly different impressions of mantle color. 2. String of pearls (or "tongue tips" by Howell/Dunn). While that seems our most reliable field mark for adults, it is worth noting that the pearls may not always be visible in the field from above, apparently related to molt, and of course is not an issue for 3rd cycle. Howell and Dunn's book has an adult bird (in the initial section, not the species accounts) that shows no apparent "pearls".
Associations with marine vessels. Slaty-backeds that show in our region very well may be in part vessel-assisted or vessel-oriented birds. As is well known, we have a vast number of container ships coming and going from Japan, n. China, and S. Korea to the US West coast. Birds following a ship can show a remarkable willingness to stay behind or aboard a vessel, sometimes feeding at the stern and then deciding to rest on board wherever open space might be found. Similarly, in the AK fishing industry, it was common to observe Slaty-b, vegae and other gulls following the boat for considerable duration, especially while processing; on a rare trip to the Russian Bering Sea in 1997, we on return brought back into US waters at 61 N, 179 E a considerable "tail" of Slaty-b and vegae which stayed close almost all the way to Dutch Harbor (normally, as in WA, laws prohibit fish processing when entering coastal waters, and so scavengers will usually diminish in number once processing has concluded). Other birds will follow the routine also: a Peregrine that boarded near Dutch in AK waters, perching in the mast, was willing to stay there and around the boat until we reached the waters off Cape Navarin in the Russian Bering Sea, five days later, at which time it flew off, surely for the Russian landmass.

It seems likely that Slaty-backed has been at times overlooked in our region, but 3 Slaty-backeds at one site would be a first for WA.

Scott Atkinson
Lake Stevens
mail to: scottratkinson at hotmail.com

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