IBRC #16-B-12

Idaho Bird Records Committee
Rarities Report Form

Species: Glaucous Gull (2 1^st-winter birds)

Reporter: Jay Carlisle, 4202 N Whitehead St., Boise, ID 83703

Other Observers: Heidi Ware

Date Report Prepared: 1/21/12

Date Sighting Occurred: 1/21/12

Locality of Observation: Hidden Hollow landfill, Boise

Habitat: settling pond adjacent to dump

Conditions: cloudy, breezy, and some showers. I used my Swarovski 10X42 binos and scope

Did you take notes? no

Did you consult a field guide or other reference work? no

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

Description: 2 very large, mostly white gulls with sharply marked, bicolored (pink and black) bills. Eyes were dark and legs were pinkish. Swimming, bathing, perched, and in flight, it was clear that primaries were all white. Both birds had subtle brown markings in the mantle area.

Behavior: Heidi first saw both birds bathing in the settling pond. One bird soon flew to shore and chased off gulls to clear an area to perch. The second bird then flew to roost in a different area among the flock. Other than a time when all gulls flushed for a moment, both stayed roosting most of the time.

How and when did you positively identify the bird, and what clinched the identification for you? Heidi first pointed out 2 “big, white gulls” and through binoculars we both saw the pink and black bills, the large size, and the pure white wings and we knew they were Glaucous. These birds dwarfed all other gulls present, including numerous Herrings and an adult Thayer’s.

How did you eliminate similar species, and what were they?

Possibilities include Kumlien’s (Iceland) Gull, which are smaller, with a more petite bill (usually more extensively dark in 1^st-W), rounded head, and longer primary projection, plus Kumlien’s that we have seen in Idaho haven’t had pure white wingtips. Another possibility would be Glaucous-winged Gull which would have darker gray wing tips, a thicker bill, and a different head shape. Hybrids are possible, but the lack of a peak on the back of the head, plus the bill shape and overall pale color pattern fit best with a pure Glaucous. Also, hybrids with any darker-winged gull species should have darker wing tips.

Experience with this species (and similar species): I have seen about probably at least 40 Glaucous Gulls of various ages. I have also seen hundreds of Glaucous-winged Gulls, including first winter birds, numerous Iceland Gulls, and many other first winter gulls of various species – including hybrids of Glaucous with Herring and Glaucous-winged.

General birding experience: 17 years of experience.

Were photo(s), video, and/or audio obtained by you? (If yes, please include or attach) Yes – digiscoped photos of each bird attached.

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