Verification of Unusual Sight Record
For Utah

Rec. # 2009-22

Common name:

Lesser Black-backed Gull

Scientific name: Larus fuscus
Date: Nov 8 & 9, 2009
Time: 9 a.m. (8th) 12 noon (9th)
Length of time observed: 20 min, 10 min
Number: 1
Age: Third winter
Sex: Unknown
Location: mile 1.1, Antelope Island Causeway
County: Davis
Latilong: Unknown
Elevation: 4200 ft
Distance to bird: 30-50 ft (8th), 300-400 yards (9th)
Optical equipment: 8 x 42 binoculars, 85 mm spotting scope with 20-60x zoom eyepiece
Weather: 50-60 degrees, high clouds, unseasonably warm fall
Light Conditions: diffused and full sun
Description:        Size of bird: Same as neighboring California Gulls
(Description:)       Basic Shape: Classic gull
(Description:)  Overall Pattern: White head, underparts, tail; slate gray upperparts and wings
(Description:)            Bill Type: gull
Field Marks and
Identifying Characteristics:
Commensurate in size to CAGUs, but with larger head and thicker neck.
Bare parts:
Bill: Yellow with red gonys spot and slight vertical black bill bar. Gonydeal angle minimal. Bill thicker than CAGU bills.
Eye: Pale yellow.
Legs and feet: Yellow, slightly stronger color than CAGUs, but sometimes took on a fleshy cast. Feet webbed.

Head: Base color white with fine but heavy dusky streaks. Dark smudge in front of eye; lighter smudge behind eye. Forehead relatively flat and tapered smoothly into bill rather than rounded as in CAGUs. Hindneck and neck-sides very smudgy; smudges spilled onto upper breast.

Upperparts: Slate gray mantle and folded wings. Shade obviously darker than CAGUs by a shade or two. White tertial crescent.
Wingtips: Black with two tiny white tips of individual primaries visible. Did not see mirror. Wingtips about equal with tail tip. In flight, trailing edge of wing appeared uniform length and white-edged.
Tail: White.
Underparts: White.
(see photos)
Song or call & method of delivery: None heard.
Behavior: Foraged while walking on shore with about a dozen CAGUs. Occasionally flew a short distance over water with other gulls and swam the several feet back to shore. On 11/9, review bird was swimming in the dispersed flock of Bonaparte's Gulls, then swam the several hundred yards back to shore.
Habitat: Shoreline of large saline lake.
Similar species and how
were they eliminated:
Three large gulls with mantles darker than CAGUs:
Not a Slaty-backed: SBGUs have pink legs and feet.
Not a Western: WEGUs have pink legs and feet, flat and shallow forehead, very heavy bill.
Not a Yellow-footed: YFGU likely to have combination of pronounced gonydeal angle, whiter head while lacking black bill bar.
Previous experience with
this & similar species:
None with review bird or comparison species.
References consulted: Olsen and Larsson, 2003.
Description from: From memory
Observer: Kristin Purdy
Observer's address: 1961 Arapaho Circle, Ogden, UT 84403
Observer's e-mail address:
Other observers who independently identified this bird: Keith Evans, Jack Rensel, John Bellmon
Date prepared: November 11, 2009
Additional material: Photos
Additional_Comments: Notes made independently of photos.