Sighting Record for Utah

Common name:	Western Gull
Scientific name:	Larus occidentalis
Date:	7/8/08, 7/10/08
Time:	7/8: about 6:30 p.m., 7/10: about 8:30 p.m.
Length of time observed:	about 8 minutes total
Number:	1
Age:	adult Alternate (breeding) /4th calender year
Sex:	unknown
Location:	Bear River Migratory Bird Refuge (south end of Unit 2 along the auto tour route)
County:	Box Elder
Latilong:	unknown
Elevation:	unknown
Distance to bird:	7/8: about 20 yards, 7/10: about 80 yards
Optical equipment:	Nikon Premier LXL 10x42 Binoculars, Swarovski ST-80 spotting scope w/20-60x zoom eyepiece
Weather:	Clear, calm, about 85 degrees F during both observations
Light Conditions:	7/8: Poor to fair with bird slightly backlit and sun at about 10:00; 7/10: Good with sun at back at about 7:00
Description: Size of bird:	Noticeably larger than nearby California Gulls (about size of American Herring Gull with which I much previous experience)
(Description:) Basic Shape:	Gull-shaped
(Description:) Overall Pattern:	Dark-mantled gull with dark, slaty blackish-gray mantle and white head, neck, breast, and belly
(Description:) Bill Type:	Thick, stout, and with well pronounced gonydeal angle
(Description:) Field Marks and Identifying Characteristics:	As previously mentioned, an adult or near-adult, large, dark-mantled gull, noticeably larger than nearby California Gulls. Rest of plumage including the head, neck, breast, and underparts was gleaming white. Body shape was also noticably bulky and thick necked/chested compared to the California Gulls, and with a noticably shorter primary projection. Bill was bright yellow-orange, thick, and stout with a noticable gonydeal angle toward the tip and a bright red gonys spot. The gape also appeared a bright yellow-orange along with the oribital ring. The eyes appeared dark brown, although not as dark as the nearby California Gulls. After analyzing photos, it was apparent that the eyes were pale-based, but with dense, dark speckling present throughout. The coloration of the legs and feet appeared fleshy pink. Wings were relatively broad-based, and were the same shade of dark, slaty blackish-gray as the mantle, and with broad white tertial and secondary tip! s. Primaries were heavily worn and appeared brownish-black with most of the white primary tips worn away. Analyzing the in flight photo, mirrors were present the last primaries (P10) and very faint subterminal spots were present on P7-P5, while the inner primaries (P1-P4) appeared to be actively growing (at least on left wing). Tail feathers were predominantly white, but showed a faint blackish subterminal markings on the inner tail feathers, which suggests that the bird is most likely a 4th calendar year in near-adult plumage. The uniformity of the dark markings making up a faint sub-terminal band on the tail suggest that the markings were actual pigmentation rather than outside staining. Also a subtle feature noted in some field guides which was well apparent on this bird in the field and in one of the photos was the drooping "skirt" of secondaries which appeared to be held loosely to the body when the bird was standing in a relaxed posture. (see photos)
Song or call & method of delivery:	None.
Behavior:	During both observations, the bird was initially seen standing amongst a loose group of 8-10 California Gulls which were congregating at an outflow channel where there were likely schools of stranded and dead fish and other aquatic invertebrates which they were likely feeding on. When approached the bird appeared very skittish and during the first observation, likely flew away from the site due to my presence. During the second observation, the bird was briefly observed washing its bill in the water before it was again observed flying away from the site, although apparently not from my presence.
Habitat:	A small outflow channel surrounded by vast, dried and active marshes. Topography was very flat with the Wasatch Mountains present off in the distance to the east and the Great Salt Lake present off to the west.
Similar species and how were they eliminated:	Slaty-backed Gull and Lesser Black-backed Gull and its assorted hybrids were most importantly elminated through the primary pattern, body and bill shape, and eye color. Great Black-backed Gull was eliminated by size and primary pattern. None of the features on this bird, including mantle color and primary pattern suggested hybridization with Glaucous-winged Gull.
Previous experience with this & similar species:	No prior experience. Although much experience with Lesser Black-backed Gull and Great Black-backed Gull plus their hybrids with Herring Gull after having actively birded the Niagara River in WNY and adjacent Ontario, Canada for 6+ years. Also some experience with Slaty-backed Gull having seen 2 birds (adult and 3rd-winter) in NYS and Ontario during the winter/spring of 2006-2007.
References consulted:	Sibley Guide to Birds by David Allen Sibley and Gulls of North America, Europe, and Asia by Klaus Malling Olsen and Hans Larsson. Additional_Comments:
Description from:	From memory
Observer:	Jim Pawlicki
Observer's address:	70 Gaslight Trail, Williamsville, New York, 14221-2207
Observer's e-mail address:	jmpawli88@aol.com
Other observers who independently identified this bird:	Matt Alexander from Portland, Oregon.
Date prepared:	8/29/2008
Additional material:	Two photos, cropped with the first slightly lightened are posted on the Utah birds website at: http://www.utahbirds.org/hotlinephotos/2008/WesternGull.htm. The two photos posted at the previous address, along with an additional in-flight shot can be found at: http://picasaweb.google.com/jmpawli88/OutWestRotation2708
Additional Comments:	Regarding subspecific identification, from what is visible in the two in-flight photos, the extent of black/brown in the spread primaries appear to favor the southern subspecies L.o. wymani over the nominate northern subspecies (Olsen and Larsson 2004), although the great deal of individual variation within gulls, along the heavy primary wear would seem to allow only limited use of primary pattern in identifying the individual to subspecies, and especially with an individual being well out of range.