Verification of Unusual Sight Record
For Utah

Rec. # 2006-60

Common name:

Western Gull

Scientific name: Larus occidentalis
Date: 12/27/2006
Time: 2:30 4:15 pm
Length of time observed: 1 hour 45 minutes
Number: 1
Age: 3rd Winter
Sex: n/a
Location: Lee Kay Ponds (5800 West 1400 South)
County: Salt Lake
Elevation: 4215
Distance to bird: 25 -150 feet
Optical equipment: 10x42 Nikon Binoculars, 20-60x80 Nikon Scope, Canon Camera w/400mm lens
Weather: Cloudy and cold with a slight breeze
Light Conditions: Overcast/Low Light
Description:        Size of bird: Large Gull (similar in size to Herring Gull)
(Description:)       Basic Shape: Gull Shaped, heavy bodied
(Description:)  Overall Pattern: White, gray and black with pink legs and a yellow-orange bill
(Description:)            Bill Type: large gull-typed bill
Field Marks and
Identifying Characteristics:
Initial thought upon seeing the bird was that it looked good for a Western Gull. The bird had a large white head with slight gray streaking in the lower nape and neck and a bit of dark feathering behind and in front of the eye, with some faint streaking on the back of the top of the head. Their appeared to be some fine streaking on the face as well, but nothing smudgy as one would expect with an Olympic Gull. The nape was completely free of any markings with just a little streaking at the back of the crown.

The eye seemed small in relation to the head and looked dark in the lighting, but the iris color was impossible to see in the horrible lighting.

The bill was massive. It stuck out among the other gulls not only due to the size, but the color. The bill was a yellow-orange with a black marking about 2/3 of the way to the tip on the lower mandible. It appeared to create slant towards the face on the upper mandible, with light black where the upper and lower touch, heading in about 1/3 of the way to the head. It created sort of a sideways T. The bottom of the lower mandible had a slight curve from the base to the gonys spot.

The front of the neck, breast, flanks, sides, belly and undertail were clean white and unmarked.

The mantle and coverts were clean gray. The gray was rather dark and noticeably darker than the nearby California Gulls. The wings were unique and had several defining marks. The secondaries appeared to have a little black the in the feathers from the body out to the primaries,
fading as the feathers got closer to the body. The primaries were black from P5-P10. P5-P7 had small white tips while there was no white in P8-10. In flight it appeared that the bird may actually be missing what should be P7 and could possibly be molting, explaining the fading black in the secondaries. The feather just inside of P5 which I guess would be P4 had a black center with a large white tip and white base. The trailing edge of the wing along the secondaries had a rather thick, clean, white stripe.

The rump was clean white.

The tail was white with a black band along the middle from side to side, probably an inch and a half thick. The tips of the tail feathers were white.

The legs were pink and appeared to be a darker shade of pink than the nearby Herring Gulls.
(see photos)
Song or call & method of delivery: No song or call heard
Behavior: Typical gull behavior. In the time spent watching the bird, it fed, slept, walked, sat and flew.
Habitat: Large freshwater pond adjacent to a county landfill.
Similar species and how
were they eliminated:
In reality there aren t any species that are similar enough to confuse this bird with. The worst case scenario would be a hybrid Glaucous-winged X Western Gull, otherwise known as an Olympic Gull . However, I will eliminate the few similar species.

Herring Gull This species has a much lighter mantle not to mention a smaller bill, yellow iris and lighter pink legs. Herring Gulls this time of year also have extensive smudging and dark streaking on the head, nape and neck.

California Gull A much smaller gull with a rather petite bill in comparison. The mantle is only slightly lighter than the Western Gull, but the bill is completely different in shape and markings. CAGU of this age typically have yellow or yellow-green legs.

Lesser Black-backed Gull A smaller gull about the same size as a California Gull, this species has a yellow iris, ALWAYS. It also shows considerable streaking on the head, nape, and neck.

Slaty-backed, Yellow-footed, Kelp, and Black-tailed all have dark mantles, but none have the summary of field marks to look even remotely like a Western Gull.

Olympic Gull This is probably the biggest problem as Western and Glaucous-winged Gulls commonly hybridize along the Pacific coast and in some locations are more common than either of the actual species. However with that said, the bird seen at Lee Kay lacked several marks common to Olympic Gulls. The head of this species is almost always heavily streaked and smudged along the nape, neck and head. This smudging is very noticeable. The bill of this species is always massive, and typically yellow with a red spot. The bottom of the lower mandible is often almost flat, with no noticeable curve on the gonydeal angle. The mantle of this species would be about on par with that of California Gull and often times much lighter depending on the individual. The primaries typically fade from gray to black at the tips, with the majority of the
primary feathers being charcoal-gray, not jet-black. Although I am not sure of what type of wing markings a 3rd winter bird would have, this species typically has a large mirror in P10.

The high rate of hybridization, and complications with back breeding, etc, make the Olympic Gulls very interesting, but also leave a high range of variability that can be very complex. However, I do believe that this bird is pure and not a hybrid due to the lack of several distinct
markings typical of Olympic Gull. Upon sharing the images with experts I received responses indicating that the bird did indeed appear to be a pure Western Gull. Their notes can be seen attached in the notes section of this report.
Previous experience with
this & similar species:
I have spent considerable time each of the past few winters at the dump studying winter gulls and am very familiar with all of the common species found in Utah this time of year. I have seen a number of Olympic Gulls and photographed several, and have seen 100 s of Western Gulls on the west coast.
References consulted: The Sibley Guide to Birds, Gulls of North American by Olsen & Larrson, and the ID-frontiers forum
Description from: Notes made later
Observer: Tim Avery
Observer's address: 1754 Garfield Avenue, Salt Lake City, Utah 84108
Observer's e-mail address:
Other observers who independently identified this bird: Colby Neuman
Date prepared: 12/27/2006
Additional material: Photos
Additional comments: Pictures can be seen on this site, and notes from several experts are at the bottom of the page. I won't put names with who said what, but this is who sent responses: Mark Stackhouse, Alvaro
Jaramillo, Steven Mlodinow, Alan Contreras, Tony Leukuring, and Cliff Weisse.

The bird was again seen the following day 12/28 only reaffirming my intial belief that the bird was a pure Western Gull.