ML303332931

Age

Not specified

Sex

Not specified

Observation details

Edit (Feb. 17, 2021): Unfortunately it is clear that the reviewers will not accept this report as a Kumlien's despite the details and discussion presented below. Therefore I've changed the ID to the less specific "Iceland, otherwise it seems unlikely my report and media will never see the light of day. Continuing Iceland Gull, clearly not a Thayer's. Slightly larger than nearby Ring-billed Gulls, and a bit bulkier build, not quite as large as an American Herring Gull. Unfortunately only seen loafing (no views of the spread wing), but the bird was quite close. Mostly black bill with some flesh coloration at the base (more extensive than I'm typically used to seeing in Thayer's). Body was quite pale whitish overall, much more so than the tan coloration I'd expect from a Thayer's. Primaries mostly white with a bit of dusky incursions in (what I believe) were primarily the outer webs. Wing coverts predominantly whitish with some dusky internal markings. Upperparts quite pale with sparse light brown mottling (no where near enough to suggest a Thayer's). Overall body patterning almost the "opposite" of a Thayer's; mostly frosted white with some caramel markings rather than mostly caramel colored with extensive frosted edges. This was probably partially due to wear. Legs and feet were a dull bubblegum pink color. Overall size and primary markings help to eliminate similarly pale first-cycle white-headed gulls such as Glaucous and (more unexpected) Glaucous-winged. This bird was smaller than I would expect for either of those two species (with the exception of perhaps an East Candadian/Greenland Glaucous). Bill was much too slender and the eye/head proportions all wrong for a Glaucous-winged. There also should have been much more pink at the base of what I would have expected to be a longer than heavier bill if it had been a Glaucous. Entirely too pale for even a bleached Herring (and structurally quite different). More specifically within the Iceland Gull complex, this individual appears to fall within the acceptable range for Kumlien's. Aside for the head and bill shape/structure which appear to be a bit on the bulky side, there is little to suggest any hybrid introgression in this bird. There are limited flight shots available of this bird in eBird (I could only find one), but they show little contrast in the primaries and a lack of a sharply contrasting dark secondary bar (all of which could/should be present or more prominent in a Kumlien's X Thayer's hybrid). The lack of "coarse patterning on [the] upperparts"(Howell & Dunn 2007 pp. 488) helps to eliminate a hybrid Thayer's as well. It was mentioned to me that some flight photos appear to show darker outer primaries and paler inner primaries. I have not seen these photos, but this sounds entirely consistent with a pure Kumlien's-type, "most have brown-washed outer primaries (especially outer webs) and whitish inners" (Howell and Dunn 2007 pp. 468). I believe this is one of the features that is consistently used to separate 'glaucoides' from paler Kumlien's. 'glaucoides' typically show consistently pale primaries whereas Kumlien's have more patterning across the primaries on the spread wing. Additionally, Thayer's tend to show consistently darker upperwing surface patterning across the primaries, so if this bird had darker coloration across both the outer and inner primaries it would seem more feasible to call it a hybrid. I could see trepidation and concern identifying this as a pure Kumlien's if the primaries were darker and the secondary bar showing higher contrast with the rest of the wing. As for the head and bill structure, there are countless examples of presumed Kumlien's included in Howell & Dunn 2007, Olsen & Larsson 2003, and in eBird that show a similar structure. I believe the features of this individual fall entirely within the acceptable range for a pure Kumlien's. Identifying it as a hybrid seems even more speculative at best, especially since Thayer's, while not currently recognized as a full species, seems to represent a more distinctive taxon with respect to Iceland than Kumlien's and reporting it more generally as an Iceland reduces the specificity and usefulness of the record in determining overall patterns of vagrancy.

Technical information

Model

Canon EOS 70D

Lens

EF400mm f/5.6L USM

ISO

1250

Focal length

400 mm

Flash

Flash did not fire

f-stop

f/5.6

Shutter speed

1/6400 sec

Dimensions

3777 pixels x 2518 pixels

Original file size

1.24 MB