Idaho Bird Records Committee Rarities Report Form
Species: Glaucous-winged Gull
Reporter: Cliff Weisse, 4125 Beaver Springs Rd., Island Park, ID 83429, 208-558-7789, cliffandlisa@octobersetters.com
Other Observers: Lisa Weisse
Date of Observation: 12/22/2004
Date Report Prepared: 11/13/2006
Locality of Observation: Pickles Butte Landfill, Canyon County, southwest of Nampa on Missouri Ave.
Habitat: Garbage Dump
Conditions:
Did you take notes…
not at all
Did you consult a field guide or other reference work?
not at all
What guide or reference did you consult?
Description (taken from photos): Large first winter gull. Body is bulky with deep chest and belly. Overall cold medium graybrown lacking strong contrast anywhere in the plumage. Bill entirely black, stout, slightly bulbous with strong gonydeal angle. Head proportionately small, rounded crown/not strongly angulated, eye small with dark iris. Neck mottled and paler than mantle or underparts. Mantle a mixture of juvenile type feathers with weakly defined bars of graybrown and dirty whitish, some scapulars replaced by unmarked medium graybrown adult type feathers that appear darker than Herring Gull and slightly paler in shade the California Gull. Lesser and median coverts evenly checkered whitish and graybrown creating the palest area on the upperparts. Greater coverts range from evenly checkered with dirty whitish and graybrown over the entire length on the inner feather to solid graybrown with faint hint of paler checkering on the outer feathers. Checkering of greater coverts is medium sized, definitely not coarse, and gradually fades from strong(inner) to weak(outer). Tertials solid graybrown at the base with paler tips and notches near the pale tip. Lower tertial with about 15 percent of tip pale, uppermost visible tertial with about 30 percent of tip pale and extensive notches on entire feather. Primary stack wide and tapered to a point. Tips of individual primaries appear centered on feather behind it, not aligned on the lower edge. Primaries have extensive pale whitish tips and pale edges extending along entire feathers, wider on inner edge of primaries. Breast and belly even graybrown. Legs kind of short and dark pink.
Behavior: Foraging at garbage pile.
How did you eliminate similar species, and what were they?
Glaucous-winged is the only large gull with 1st winter plumage that's medium graybrown overall with primaries and tertials concolor with the rest of the upperparts. Herring, Thayer's, Great Black-backed, Lesser Black-backed, Western, California, Ring-billed all have dark brown or blackish primaries that are darker than the rest of the plumage. Glaucous has whitish primaries and strongly bicolored bill with bright pink base and black tip. Iceland has paler, more heavily chckered plumage, concolor or paler primaries, pale centered tertials, and short, petite bill with weak gonydeal angle. Glaucous-winged is far more likely to be confused with hybrids of Glaucous-winged x Western or Herring Gull. Either combination would produce primaries that are darker than the rest of the plumage and typically a narrower primary stack with lower edge aligned when perched. They also typically produce more strongly patterned plumage, especially wing coverts. This individual has field marks that are entirely consistent with that typical of Glaucous-winged Gull in first winter plumage. There are no marks that suggest hybrid origin.
Experience with this species: I have seen approximately 10 Glaucous-winged Gulls in Utah and Idaho as well as quite a few in California. I have also seen a number of Glaucous-winged x Herring and Glaucous-winged x Western Gulls. I spend time birding garbage dumps and see thousands of gulls annually. Most are Ring-billed and California but Herring is annual in numbers up to 100 (Utah) as is Thayer's (up to 8 individuals in Utah). I've seen a few Lesser Black-backed, Mew, and Glaucous and hundreds of Great Black-backed in NJ. I've studied Gulls seriously for the past seven or eight years.
General experience birding: 13 years
Were photo(s), video, and/or audio obtained by you? yes
