ML126509771

Age and sex

Immature Unknown sex - 1

Observation details

(Originally recorded as Slaty-backed Gull, with these notes) Relocated from a sighting a few minutes earlier at the Logan Fish Hatchery. I wasn't able to photograph the bird until I relocated it here, so that earlier sighting has no photos. This was my 253rd species in Cache County this year. Full write-up is available here: http://www.utahbirds.org/RecCom/2014/2014_003.htm Would have been first state record if accepted, but the UBRC decided that Slaty-backed Gulls cannot be distinguished from Glaucous-winged x Herring Gull hybrids in their first winter. This is in contrast to the opinions of several well-reputed gull experts, for example: "The underwing seems to have the 'shaggy' look I have come to associate with juvenile Slaty-backed. The bill and head shape, short tibia, and bulging chest look great, and the plumage fits well. Many Slaty-backeds have white interior markings in the innermost greater coverts, making them less distinctive, but this one has a classically solid SBGU panel that may well be outside the range of variation of Glaucous-winged x Herring hybrids. . . . There are two Slaty-backed Gulls on this page of the Japanese Gull-Site (2nd page of first cycles) that have darkish, non-contrasting rumps/uppertail coverts, just like your bird. This is obviously an extremely variable character. With that concern out of the way, I'm much more comfortable with it being a Slaty-backed. The resemblance of some Glaucous-winged x Herring hybrids to young Slaty-backed has discouraged most people from identifying SBGUs of this age in the lower forty-eight. See Steve Hampton's page for good discussion and photos of this problem. Many birds are probably best left alone. However, the Utah bird just happens to have several features--exhibited by some but not all Slaty-backeds--that do not make sense for any such hybrid. The structure and upperwing coverts are quite unlike anything I've seen in GW x Herring hybrids (or either parent species). Hampton has photos of one apparent GWxH hybrid with plain greater coverts, but it does not have a distinct Slaty-backed structure as in your bird." -Tristan McKee, California Bird Records Committee emeritus "Wow-- I think the scaps and coverts look really good [for SBGU], like the birds at http://harrisbirds.com/Slaty-backed%20Gull.htm. I really like the pale line of dots at the bottom of the median coverts. Body, head, and bill shape are good too." -Steve Hampton, author of the gull identification website at http://www.tertial.us/gulls/gulls.htm Note added May 2023: Now nearly 10 years later, I've revisited this gull in the context of Jaramillo's 2020 article on first-winter Slaty-backed Gulls in Japan, and I have renewed doubts. First, this bird just seems excessively dark. Importantly, the greater secondary coverts are almost solidly dark, and pale greater secondary coverts seem to be among the more reliable identification features that should be evident in these photos. Second, although the rump is photographed at a difficult angle, it seems to be pretty dark, well-checkered throughout. I wish I could feel comfortable calling this a Slaty-backed Gull, but even after ten years I have some hesitation, and I'm now leaning a bit in the "HERG x GWGU" camp, so I'm conservatively changing this to "Larus sp."

Technical information

Model

NIKON D90

ISO

800

Focal length

400 mm

Flash

Flash did not fire

f-stop

f/7.1

Shutter speed

1/2000 sec

Dimensions

2310 pixels x 1627 pixels

Original file size

1.13 MB