Regardless, after dropping my daughter off at school this morning I wound my way back home to pick up a few things for work. A quick walk around the yard to lighten my melancholy yielded dozens of waxwings (none Bohemian), two laden crab apple trees (no Pine Grosbeaks), and mostly filled feeders (no redpolls to be confused with Hoary). Sigh.
The daily commute was just as uneventful. No shrikes, no Rough-legged Hawks; nothing, really, but starlings and pigeons. Long sigh.
Nothing new while walking through the parking lot into the Lab - until I saw four hardcore birders racing to their car and peeling out. Something was up, so I raced upstairs to check the listserve. There, after booting up the computer, I discovered . . . nothing. "Connection not found." Sheeesh (confession: I didn't really say "sheesh," but something a little more R-rated). Deal with that later, off to a different computer on a different network. Start Firefox, head to Gmail . . . username . . . password . . loading . . .still loading . . . and there it finally was, right in the subject line
"Probable Slaty-backed Gull at compost pile."
Simple, straight-forward; the next post was better: it dropped the "probable."
So, off I went (after using eBird to find out where the compost pile was, I'd heard of this place but never been there). Upon arriving I found six or so birders, dozens of crows, hundreds of gulls to sort through . . . Great Black-backed, Herring, Ring-billed, a single Lesser Black-backed . . . and a scope set up, pointed at a sleeping Slaty-backed. In the twenty minutes I stayed I didn't see the bill or the legs, but you could note some characteristic features: the overall size, the blocky head; the fact that some of the best birders already identified it.
Later, pictures began to surface from Kevin McGowan, Tim Lenz, and Tom Johnson (click on their names to view their galleries). Tom followed up with a careful analysis posted on Cayugabirds (our local listserve), where he noted, "Everything is great for a subadult (likely 3rd cycle) Slaty-backed Gull with the possible exception of the relatively pale upperparts."
He continued (lariphobes may want to skip this part),
I was able to directly compare the bird to an adult graellsii Lesser Black-backed Gull (LBBG), and noted that the Slaty-backed Gull (SBGU) generally appeared lighter than the LBBG, though this varied. Occasionally the Lesser Black-backed Gull and Slaty-backed Gull appeared to have identically shaded mantles, but this varied with the angle at which the birds were standing relative to the light and me. Variation in upperparts shading has been a subject of debate and study for a while now, and two articles are particularly relevant (citations below). The first is a 1994 article in Birding by Gustafson and Peterjohn that suggests wide variability in upperparts coloration in Slaty-backed Gull.
However, in 1999, King and Carey suggested in Birder's Journal that the Gustafson/ Peterjohn assessment of variability was not accurate, and that overall, Slaty-backed Gull upperparts are somewhat uniform in coloration, with a small degree of variation ranging between the coloration of graellsii (lighter end) and intermedius (darker end) Lesser Black-backed Gull (Larus fuscus). They suggest that Slaty-backed Gulls with upperparts paler than graellsii should be examined for signs of hybridity and that the paler specimens examined for the Gustafson/ Peterjohn article likely represented hybrids.
Slaty-backed Gulls have been found to hybridize with Glaucous-winged and Vega Gulls in northeastern Asia. Anyway, aside from pale upperparts, I found nothing on the Ithaca bird today consistent with a hybrid. The small apical spots on the outer primaries combined with dull, somewhat brownish greater and primary coverts and the dark bill suggest a third (or possibly) fourth cycle gull.
Here are the citations for those articles:
- Gustafson, Mary E. and Peterjohn, Bruce G. 1994. Adult Slaty-backed Gulls: Variability in Mantle Color and Comments on Identification. Birding 26(4):243-249.
- King, Jon R. and Carey, Geoff. 1999. Slaty-backed Gull hybridization and variation in adult upperparts colour. Birder's Journal 8(2):88-93.
The bird was watched for a couple of hours by various birders, then it headed off to who knows where.
Until it was discovered in the late afternoon at Stewart Park (Ithaca), south end of Cayuga Lake, where hundreds (if not more) gulls roost every night. This is a daily pattern: the gulls roost on the lake, head somewhere to feed during the day, often the compost pile, and then back to the lake in the evening.
I'm anticipating a stop on my way in tomorrow, at the lake or the compost pile; this time I'll plan some digiscoping of my own.
I'm definitely in the mood.