For the last several years, two gull species from eastern Asia, Slaty-backed Gull and Black-tailed Gull, have been on the short list of expected new birds for Ohio.We’ve wondered which one would turn up here first.There have been a couple of tentative sightings of possible Slaty-backeds, but Craig Holt nailed a definite Ohio Black-tailed Gull two weeks ago, and hundreds of birders have had a chance to enjoy it since.

It’s interesting to compare the status of these two east Asian gulls in Alaska.Slaty-backed Gull is regular in western Alaska in summer, mainly in the Bering Sea region.When I was leading Alaska tours, we could almost always find a few Slaty-backs around Nome, and often at Gambell or St. Paul.By contrast, Black-tailed Gull is still considered very rare in Alaska; there are more than two dozen records for the state, mostly for western and southern Alaska, but it is not regular anywhere there and not seen every year.

When the first Slaty-backed Gull for the lower 48 states was found (December 1983 – January 1984 at St. Louis, Missouri), it created quite a stir.But few people questioned its status as a genuine wild stray, because the species already had an established pattern of occurring in western and southern Alaska.By contrast, the first Black-tailed Gull for North America (at San Diego in November 1954) was assumed at the time to have been ship-assisted, because back then there were no Alaskan records at all.Thirty years later, when another Black-tailed was found – in Maryland, in July 1984 – many nearby birders didn’t even bother to go look at it, because it was assumed that the bird must be an escapee from captivity, or assisted by humans in some other way.Only later, after records began to accumulate in Alaska and elsewhere, did people start to have second thoughts about the San Diego and Maryland individuals.

There are now scores of records of Slaty-backed Gulls all over North America outside of Alaska, south to Texas and east to Newfoundland, with records thinning out as one moves away from the northwest.A high percentage of these are adults and third-cycle birds; younger birds may be often overlooked because of identification challenges.

Records of Black-tailed Gulls show a different pattern.There are now more than three dozen records outside of Alaska, many scattered around eastern North America, but it’s possible that many of the records could involve the same individuals being re-found at different places.For example, repeated records in Virginia and Rhode Island during 1995 and 1996 all could have referred to one individual. Records during summer 2003 in Wisconsin, Illinois, and Indiana probably all referred to one individual. The bird currently at Ashtabula could be the same bird that was at Port Burwell, providing a first record for Ontario, in fall 2009.Of course, that doesn’t diminish the excitement of seeing it here!But the pattern of records suggests that the occasional Black-tailed Gull strays to eastern North America and then wanders around this general region, perhaps for years, rather than returning to its native range, and these long-term exiles are then occasionally found by birders.

One other pattern that emerges is that these Black-tailed Gulls in North America often stay in the same general area for weeks at a time.So there’s a good chance that our distinguished visitor could continue at Ashtabula for some time yet.

Kenn Kaufman
Editor, Kaufman Field Guides series
http://www.kaufmanfieldguides.com/
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