Path: utzoo!attcan!uunet!ginosko!gem.mps.ohio-state.edu!usc!apple!brutus.cs.uiuc.edu!psuvax1!rutgers!sunybcs!joey.cs.buffalo.edu!dmark From: dmark@joey.cs.buffalo.edu (David Mark) Newsgroups: rec.birds Subject: Re: What is this bird?? Message-ID: <10772@eerie.acsu.Buffalo.EDU> Date: 23 Sep 89 14:06:06 GMT References: <3791@helios.ee.lbl.gov> <48214@oliveb.olivetti.com> <3192@nmtsun.nmt.edu> Sender: nobody@acsu.buffalo.edu Reply-To: dmark@joey.cs.buffalo.edu.UUCP (David Mark) Distribution: na Organization: SUNY @ Buffalo Lines: 46 In article <3192@nmtsun.nmt.edu> john@nmtsun.nmt.edu (John Shipman) writes: > >While we're on the subject of nasty field identification >problems, how about hybrids? The Christmas Bird Counts >from the northern Pacific coast in the last few years >often list more Glaucous-winged x Western Gulls than >either of the unhybridized species. How are they >calling this form? A phenotypically pure glaucescens has no black whatsoever in the wings. Essentially all of the big gulls breeding on the British Columbia coast on the "inside" of Vancouver Island, and north of Vancouver Island, are like this. But, on the "outside" of V.I., a small proportion have black or very dark areas on the upper side of the primaries. I went out to Cleland Island off Tofino with Mike Sheppard, then of the Provincial Museum, to band gulls. There were 3 phenotypically-pure "occidentalis" types among the several thousand "glaucescens", two "occidentalis" paired to eachother and not breedings, the other paired to a glaucescens. I recall that I estimated about 1-2 % of the gulls there appeared to be hybrids. Around Westport, Washington, in summer, it is very hard to find "pure" occidentalis *OR* glaucescens, with most birds being intermediate. Frankly, I don't understand why they have not been lumped. It is obvious that the GULLS don't care about the difference. Hoffman, Wiens, and Scott (Auk 95:441-456, 1978) studied the hybridization along the Washington Coast, and found that hybrid pairs had higher breeding success than pure tryue-to-type pairs. In color, adult "gloccidentalis" birds resemble thayeri. Primaries are dark above but not below, dark iris. But the 'jizz' is quite different, with thayeri adults being rather 'delicate', looking almost like large Mew gulls, or at least like Californias, whereas 'gloccidentalis' are big bulky birds with large long bills, flatter heads, etc. Another hybrid that occurs around Vancouver BC in winter is HerringXGlaucous-w. These also have a similar phenotype to the above hybrid and to thayeri. They come from Cook Inlet area, when interior Herring types spead from dump to dump out to the coast. Once, I saw an adult, color-banded gull near Vancouver, which had this dark-above, light-below pattern on the primaries. I sent in the color pattern to the banding office and it turned out to have been banded as a chick in the Cook Inlet area. Obviously, observers in southern California or the southwest, who perhaps are unfamiliar with thayeri, should be cautious in identifying adult gulls with the primary pattern mentioned above as Thayer's Gulls. David Mark dmark@cs.buffalo.edu