Sighting Record for Utah

Common name:	Western Gull
Scientific name:	Larus occidentalis
Date:	11/16/2021
Time:	1:45pm
Length of time observed:	20 minutes
Number:	1
Age:	Hatch Year
Sex:	?
Location:	Pond north of Bountiful Dump at Farmington Bay WMA
County:	Davis
Latilong:	40.917550, -111.914495
Elevation:	4200
Distance to bird:	300m
Optical equipment:	Kowa 88mm spotting scope
Weather:	partly cloudy, breezy, 50F
Light Conditions:	Good when sun in clouds, poor when sun out due to heat shimmer
Description: Size of bird:	Large gull
(Description:) Basic Shape:	typical gull
(Description:) Overall Pattern:	uniform dark brown
(Description:) Bill Type:	heavy gull bill
(Description:) Field Marks and Identifying Characteristics:	"1st cycle bird, prominent large droopy bill with significant gonydeal angle, pale nape with dark sooty mask, sooty gray brown back, prominent secondary skirt with black secondaries that had a white trailing edge, black primaries with very short projection past tail. Slightly smaller than HERG with more compact structure. Briefly flapped wings had a whitish rump and all black flight feathers." from notes taken at time of sighting, I studied this gull in the scope for a very long time, and actually recorded myself on my phone describing the bird in real time so I could transcribe to my notes what I was seeing. Photos extremely poor due to distance but do show the bill shape and overall structure of the bird (see photos)
Song or call & method of delivery:	none heard
Behavior:	Swimming in a large group of gulls on the far side of the pond. At one point started preening, also got up and fought with a cormorant over a tiny island but lost
Habitat:	Open freshwater pond next to a dump
Similar species and how were they eliminated:	Most likely to be confused with 1st cycle Herring Gulls, many of which were present, this bird however stood out as very different, mainly by its structure. What first caught my eye was the large droopy bill with a noticeable gonydeal angle. The bill looked thicker and seemed to curve downward with a bulbous tip. Herring can have a large bill, but never the droopy bulbous tip. Also structurally the bird seemed smaller but more compact than the Herrings, with a very prominent "secondary skirt" and short primary projection past the tail. Herring have a flat back line with the primaries not separated from the back by the secondaries and tertials, this gull had fluffed up secondaries and tertials, with a very short primaries sticking past the tail, separated from the back. Overall the plumage was different as well, the back was slightly darker sooty gray than the smooth gray of the Herrings. Herrings are variable but never have the dark masked look this gull had. Also Herring have a pale window in the inner primaries that is not black, unlike the all uniform black flight feathers of this birds. Typically (American)Herring do not have a white rump either. 1st cycle California Gulls are also similar in plumage but very different in structure, with a very long primary projection and lacking the "secondary skirt" as well as having a much smaller bill that is usually bicolored, unlike this bird. A few 1st cycle California's were also present for direct comparison, they were noticeably smaller as well. Hybrid Glaucous-winged Gull X Western also should be considered and are similar in structure, but the primaries and secondaries should not be jet black, they should be some shade of gray, depending on what mixture it has. This birds primaries and secondaries were jet black so no indication of it being a hybrid.
Previous experience with this & similar species:	Yes, many of all age groups
References consulted:	Macaulay Library, Sibley app
Description from:	Notes taken at the time of the sighting From photo(s) taken at the time of the sighting
Observer:	Bryant Olsen
Observer's address:	84102
Observer's e-mail address:	**
Other observers who independently identified this bird:	None that I know of
Date prepared:	11/17/21
Additional material:	Photos
Additional comments:	eBird checklist: https://ebird.org/checklist/S97681690