Verification of Unusual Sight Record
For Utah

Rec. # 3-2001

Common name:

Glaucous-winged Gull

Scientific name: Larus glaucescens
Date: 12 Nov 2000
Time: 3:30 - 4:00 pm
Length of time observed: 30 minutes
Number: 1
Age: juvenile/1st winter
Location: Farmington Bay WMA
County: Davis
Distance to bird: 30 meters
Optical equipment:  
Weather: cloudy, light snow falling
Light Conditions: overcast, dim
Detailed description of bird: This was a large, bulky gull with a large flat forehead. A very large all black bill with a distinctive sharp gonydeal angle. Uniform all brown body plumage including primaries and tail which were the same brown color as the rest of the body plumage. The Gull had a uniform pattern of pale markings or fringes running across the lesser and median wing coverts. Pale spots were throughout the scapulars. Pale fringes visible on tips of primaries. Pink legs, dark eye.
Song or call & method of delivery: None.
Behavior: Sitting still at the edge of water impoundment
Habitat: Farmington Bay, open water, wetlands
Similar species and
how were they eliminated:
   Glaucous Gull: 1st winter. 2 toned bill - pale base with black tip. Overall body plumage paler (almost white) with coarser & more irregular pattern of markings on scapulars. paler primaries contrast with rest of the body plumage.
   Thayers gull: 1st winter: Smaller bill, smaller more rounded head. Primaries darker than mantle. dark band on tail, darker than rest of the upper body plumage.
Herring gull: 1st winter: Dark brown primaries and secondaries contrast with rest of body plumage, Dark tail, Dark barred rump.
   Glaucous-winged - Western hybird: This is a possibility. Even though this is a darker brown gull than other glaucuos-winged I have seen (There is variability in color among juvenile/1st winter birds) it is still uniform color, shape, and specific characterisitcs of a Glaucous-winged gull. A hybrid would probably show somewhat darker wingtips than the rest of the body plumage, with a less flat forehead and generally have more integration of characteristics of the 2 hybridized species. This is assuming of course that both parents were pure birds of their respective species.

Through my literature search it became apparent that hybridization of Glaucous-winged gulls with Western, Herring, and even Glaucous gulls is common. In fact, some populations in Washington are mostly hybrids and backcrosses with very few pure birds (glaucous-winged/Western).

While the gull described and photographed fits very closely the description of glaucous-winged gull it may in fact not be a pure bird because of hybridization and or backcrossing from the distant past.

Previous experience with this & similar species: I have seen several apparent Glaucous-winged gulls on the pacific coast and a few in Utah the past several years.
References consulted: P.J. Grant: Gulls a guide to Identification. Second edition. 
The Sibley Guide to Birds.
Description from: Notes at time of sighting.
Observer: Terry Sadler
Observer's address: 887 Germania Ave. Murray, UT 84123
Observer's e-mail address:
Other observers who independently identified
this bird:
Date prepared: 27 Dec 2000
Additional material: Photo, Original Document

Go to Main List of Sighting Under Review