This afternoon, Patricia Lindsay and I identified a juvenile Thayer's Gull at Argyle Lake in Babylon village, southwestern Suffolk County, Long Island.
This hatching-year Larus retained full juvenile plumage. At this date this is expected for Thayer's and Iceland Gulls, not unusual in Lesser Black-backed Gulls, but would be extremely rare in smithsonianus Herring Gulls, all of which we saw today had replaced their juvenal scaps and mantle feathers with formative feathers. The focal bird was smaller, smaller-billed, and rounder-headed than smithsonianus. The bill was also darker than on any same-aged Herring Gull seen today, generally appearing all black (but showing subtly paler base on good, close looks). The folded wingtip and tail appeared black, the dorsal-aspect primaries tipped with fine, creamy chevrons. The blackness of these feathers was far beyond any dark-end kumlieni Iceland Gull in my experience. In addition to the points mentioned above regarding structure, molt, and bill color, this bird differed from smithsonianus Herring Gull in showing a pale, Iceland Gull-like underwing pattern. This was clearly visible on my best scope views of the undersides of the wingtips when perched, and in excellent binocular views in flight. Unfortunately, the bird changed position on the rooftop immediately after my initial studies of it and before I began photographing it. Thus, the photos show only a hint of the extensively pale inner webs of the primaries, and incomplete views of the retained juvenile dorsum. Both of these things were seen previously, however, and conformed to the descriptions above. All photos were taken 1:49-1:52 EST, at which point all of the gulls in the area went up due to a bread-scattering event on the other side of the lake. I had great views of the bird in perfect light as it flew east to west the north of us, but Pat was not on it with the Lumix when it flew, so no flight shots. We lost track of it as the flocks milled around over the lake and could not re-find it. Photos can be seen here: https://flic.kr/p/2hPTG9s Shai Mitra Bay Shore -- NYSbirds-L List Info: http://www.NortheastBirding.com/NYSbirdsWELCOME.htm http://www.NortheastBirding.com/NYSbirdsRULES.htm http://www.NortheastBirding.com/NYSbirdsSubscribeConfigurationLeave.htm ARCHIVES: 1) http://www.mail-archive.com/nysbirds-l@cornell.edu/maillist.html 2) http://www.surfbirds.com/birdingmail/Group/NYSBirds-L 3) http://birding.aba.org/maillist/NY01 Please submit your observations to eBird: http://ebird.org/content/ebird/ --
