Verification of Unusual Sight Record
For Utah

Rec. # 2010-07

Common name:

Lesser Black-backed Gull

Scientific name: Larus fuscus
Date: 5 January 2010
Time: 20 minutes
Length of time observed:  
Number: 1, see note below
Age: adult
Sex: unknown
Location:  "Fishing Pond" at Lake Park. This pond is approximately 1/4 mile ast of the interesction of 5600W and 2700S and roughly between Lee Kay Ponds and Decker Lake.
County: [Salt Lake]
Latilong: ?
Elevation: ?
Distance to bird: 50-75 Yards
Optical equipment: nikon 10x42 Premier LX and Swarovski 80mm HD scope with 20-60x eyepiece
Weather: sunny and calm with little to no wind.
Light Conditions: I was on the west side of the pond with the sun behind me and slightly to the side. The low sun angle from behind made color discernment excellent.
Description:        Size of bird:  
(Description:)       Basic Shape:  
(Description:)  Overall Pattern:  
(Description:)            Bill Type:  
Field Marks and
Identifying Characteristics:
Dark mantled adult gull slightly larger than California Gull in direct comparison with birds very close together. Mantle was obviously darker than California but with obvious contrast between the black primaries and dark gray mantle. Body slender similar to California Gulls with long primary extension beyond tail. This individual appeared to be in primary molt and was missing/growing P9 (mirror on P10 is visible on the folded wing in blurry photo). Head crisply streaked with brown heaviest around eye creating shadow effect. Streaking covered head, neck and upper breast. Bill narrow with weak gonydeal expansion and proportionately shorter than CAGU, yellow with red gonydeal spot and narrow vertical dusky bar behind and above red spot. Primaries black with subterminal mirror on P10. Iris yellow. Leg color not seen.
(see photos)
Song or call & method of delivery: N/A
Behavior: Sitting on water for entire time of observation.
Habitat: Pond
Similar species and how
were they eliminated:
The dark mantle elimantes all large gulls except:
-Slaty-backed Gull has darker mantle, bulkier body, shorter primary extension, and larger bill with stronger gonydeal expansion.
-Western Gull is larger and has much larger bill with strong gonydeal expansion, shorter primary extension, shows obvious secondary skirt, and has a dark iris.
-Kelp Gull is larger with bulkier body, shorter primary extension beyond tail, darker mantle, darker iris, and heavier bill with stronger gonydeal expansion.
-Great Black-backed Gull is much larger with much larger and heavier bill, dark iris, shorter primary extension, and darker mantle.
Previous experience with
this & similar species:
I've been birding approximately 17 years and have studied gulls seriously for the past ten years in Idaho, NJ, and Utah. I've seen LBBGs almost annually, usually multiple individuals, for the past six years or so.
References consulted: Gulls of North America, Europe and Asia, by Klaus Malling Olsen and Hans Larsson
Gulls of the Americas by Steve N. G. Howell and Jon Dunn
Description from: Photos.
Observer: Cliff Weisse
Observer's address: 4125 Beaver Springs Rd., Island Park,  ID  83429
Observer's e-mail address:
Other observers who independently identified this bird:  
Date prepared: 24 January 2010
Additional material: Photos
Additional_Comments: I observed three adult LBBGs at Decker Lake about 30 minutes before the observation described in this report. Since this individual was not present when I arrived it's possible that it's one of the adults I saw at Decker Lake. I can not say for sure based on my recollection of the Decker Lake birds but it's definitely a possibility.