But this was no ordinary chase. This was a bird (Slaty-backed Gull) we've been thinking about for many years now, but haven't even had a candidate to chase after anywhere in Michigan. The only existing Michigan record is from 1981, a one day wonder at the Sault Ste. Marie dump which was not chasable. This bird has provided little solace. Especially in light of the rash of recent records in the Great Lakes region, notably multiple records from Minnesota and Wisconsin, and at least one from the Illinois/Indiana area of Lake Michigan. Anyway, not a few of us state listers have dreamt of finding our own adult Slaty-backed Gull at our local dump. It just seems SO identifiable, and just a matter of time. But in this case, Dan Duso of the Saginaw Bay area found himself in this enviable position while birding the Republic Landfill near Standish, Bay County, 2 days ago. His initial reports and photos of a possible Slaty-backed Gull started to trickle out on the 13th, and the first chasers arrived on scene yesterday, posting these tantalizing photos which appeared to clinch the ID issue (with a mantle this dark one really only had to assess the extent and position of white in the outer primaries to make a confident ID).
So, the chase was on. I arrived mid-morning and was able to get some pretty amazing views as this bird hurtled over the dump with 1000+ Herrings, ~10 Glaucous, 1 Great Black-backed, at least 2 Iceland Gulls, and a handful of Ring-billeds:This was a long-awaited life bird for me, and will represent a 2nd state record if accepted by MBRC. I won't go to the mat on ID other than to say that every assessable field mark I checked appeared to be pretty classic for Slaty-backed Gull. In terms of age, it may not be quite fully adult, as evidenced by the dusky bill and obvious brownish cast to the primary coverts and primary bases. The tail of this bird conclusively shows no black (we had thought from Dan Duso's initial photos that it did have some black). So it could plausibly be either only a 4Y bird which has not quite reached full definitive plumage (like some Great Black-backeds often do), or a full adult (=after third year [ATY]). Pyle Guide II mentions that 4Y (of which less than 5% are assignable confidently to this category) is best identified by "outer primary coverts with more extensive blackish markings" (vs. slate gray or with "limited blackish on outer webs" in A4Y), and small p10 mirrow with no p9 mirror (vs. either just p10 or both p9 and p10 with "distinct white mirrors".) I don't think we have enough to confidently call this a 4Y, but would like to hear others' opinions. Here is today's eBird checklist:
Kudos to Dan Duso for finding this amazing record, Myles Willard and others for checking up on it, and getting the word out, and to Karl Overman for being sure we all knew about it.