Rare Bird Report #: 104-B-07

Idaho Bird Records Committee Rarities Report Form

Species: Glaucous-winged Gull

Reporter: Jay Carlisle

710 N 20^th St

Boise, ID 83702

jaycarlisle@boisestate.edu

Other Observers: Bruce Ackerman

Date Report Prepared: 11-30-07

Date Sighting Occurred: 11-9-07

Locality of Observation: CJ Strike Dam, border of Elmore & Owyhee Counties

Habitat: dam and reservoir

Conditions: partly cloudy, SW breeze 10+ coming up over dam; I used Swarovski EL 10x42 binoculars and a Fujinon 80mm spotting scope (20-60 zoom) at between 20-60x.

Did you take notes? not at all

Did you consult a field guide or other reference work? during the observation

What guide(s) or reference(s) did you consult?

Sibley & National Geographic

Description: An apparent 3rd winter Glaucous-winged Gull sitting below CJ Strike dam. See the 2 pictures (very poor quality – taken thru my scope with a cheap digital) of this bird attached.

The bird was large (Herring Gull size or larger), had a large yellow bill with a dark spot near the end, and had brownish streaks/smudging on the head and chest characteristic of winter birds (appearing quite dirty from a distance). The upperwings were uniformly medium-gray with slightly darker gray in the outer primaries (less contrasting than a Thayer's Gull adult would be).

Behavior: It was mostly roosting/loafing in the vicinity of a group of gulls (including Ring-billed, California, and Herring) just below the dam. It spent some time perched on the dam, some time flying, and some time roosting on the river below the dam.

How and when did you positively identify the bird, and what clinched the identification for you? ID was clinched by large size, large bill, pale mantle color, pale wingtips (only slightly darker than mantle), and the brownish streaking/smudging on the head and chest.

How did you eliminate similar species, and what were they? Possibilities include Herring (dark wingtips), Thayer’s Gull (smaller size, darker wingtips, smaller bill), Glaucous Gull (paler wingtips, limited streaking), and hybrids. All fieldmarks suggested pure lineage – especially the extensively smudged head and neck and relatively pale wingtips.

Experience with this species (and similar species): I have observed hundreds of Glaucous-winged Gulls (all ages) along the west coast (especially Washington), including others at CJ Strike in both 2005 and 2006. I have observed countless Herring, large #s of Thayer’s (especially in winter in Oregon but many inland sightings from Idaho to South Dakota), and numerous Glaucous Gulls (Alaska, Idaho, South Dakota, etc.). I have also observed a number of apparent Western x Glaucous-winged hybrids on the west coast – but I am not an expert on gull hybrids.

General birding experience: extensive; 14+ years in US and Latin America

Were photo(s), video, and/or audio obtained by you? (If yes, please include or attach) Yes – 2 poor-quality images attached.