Idaho Bird Records Committee Rarities Report Form

 

Species: Glaucous-winged Gull

 

Reporter: Jay Carlisle

Idaho Bird Observatory, Boise State University, 1910 University Ave., Boise, ID 83725; jaycarlisle@boisestate.edu

 

Other Observers: Heidi Ware (found the bird)

 

Date Report Prepared: 3-5-09

 

Date Sighting Occurred:  3-3-09. 

 

Locality of Observation: Pickle’s Butte landfill, Canyon Co.

 

Habitat: garbage dump

 

Conditions: p cloudy to cloudy (eventually rain & hail), calm to light breeze but gusts as storm cell moved in; I used Swarovski EL 10x42 binoculars and a Fujinon scope with 20-60x zoom

 

Did you take notes?  not at all

 

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

           

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

Sibley & National Geographic – as well as various websites

 

Description:  An adult Glaucous-winged Gull in alternate plumage. 

 

The bird was larger than nearby gulls (including a Herring and many adjacent Californias and Ring-bills) and had a large yellow bill with a red gonydeal spot and a more distal and small black spot.  The mantle was medium-gray (a shade or 2 darker than a nearby Herring and maybe a shade lighter than nearby Californias) with darker gray in the outer primaries.  Other features included a heavy build, rounded head shape, pink legs, and brown eyes.

 

Behavior:  Seen roosting, in flight, and actively feeding in garbage over the course of ~ 2.5 hours.

 

How and when did you positively identify the bird, and what clinched the identification for you?  The initial clues were the size and relatively pale outer primaries.  ID was clinched by the combination of large size, dark eyes, pink legs, large bill, and pale wingtips (only slightly darker gray than mantle).

 

How did you eliminate similar species, and what were they?  Possibilities include Herring (black wingtips), Thayer’s Gull (smaller size, darker wingtips, smaller bill), Glaucous Gull (paler wingtips), Iceland Gull (smaller size, smaller bill, paler eyes) and hybrids – especially with Western Gull.  Fieldmarks we observed – especially the relatively pale wingtips – are consistent with Glaucous-winged Gull.  A hybrid Glaucous-winged x Western adult would be expected to have darker primaries than this bird.

 

Experience with this species (and similar species):  I have observed hundreds of Glaucous-winged Gulls (all ages) along the west coast (especially Washington), including other adults and 3rd-winter birds at CJ Strike dam from 2005-09 – this is my first alternate-plumaged adult in Idaho!  I have observed countless Herring, large #s of Thayer’s (including many adults, especially in winter in Oregon but many inland sightings from Idaho to South Dakota), and numerous Glaucous Gulls (Alaska, Idaho, South Dakota, etc.).  An adult Iceland Gull was found and seen well by both observers on the same day as this sighting.  I have also observed a number of Western x Glaucous-winged hybrids on the west coast – but I am not an expert on gull hybrids.

 

Heidi had seen an adult GWGU that wintered (is wintering? – 2008-09) at CJ Strike dam on 3 occasions.

 

General birding experience: extensive; 15+ years in US and Latin America

 

Were photo(s), video, and/or audio obtained by you? (If yes, please include or attach)    Yes, several.