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Documentation of Lesser Black-backed Gull
2005-166

Observer Information

Reporter:  Nicholas Komar 
Other Observers:  None; I am original observer

Species, Date, Time and Location Information

Species:  Lesser Black-backed Gull
First Date/Time:  10/11/2005
Last Date/Time:  10/11/2005
Duration (total time in view):  10 minutes
County:  Larimer
Specific Location:  Larimer County Landfill, west side of Taft Hill Road, about 1 mile south of intersection of Taft Hill Rd and Harmony Rd.
Number:  1
Age:  Unknown
Sex:  Unknown
Plumage:  Other/Unknown

Habitat

Temporary puddle at base of Ladfill along entrance road.

Viewing Conditions

Optics:  Kowa TSN-4 Telescope, 15-60 power; photographed with Nikon Coolpix 5700 through telescope.
Distance:  50 feet
Light:  Excellent light

Description of the Bird

A brown mottled immature gull the size of a California Gull (Larus californicus) with a completely black bill. Underparts were mostly pale brown, with the lower belly area approaching whitish. Head uniformly brown, with some paler areas around base of bill. Back and folded wings mottled, and dark chocolate brown scapulars edged narrowly with whitish, a few of these were centered with black. Some of the mantle feathers were dark gray (suggesting the mantle color of adult L. f. graelsi). Tertials were very dark brown, approaching black. Primaries were blackish. This bird was seen briefly in flight, and was long-winged, with wings appearing dark chocolate brown, and lacking a noticeable pale window among the inner primaries. The rump or base of tail was whitish.
Behaviors: Lounging in a large puddle with other gulls.
Call: not heard
Plumage: juvenal

Similar Species Discussion

Herring Gull and closely related species (such as Yellow-legged Gull) would be larger, with pale windows among inner primaries, and lacking dark gray and blackish feathers on mantle.

Great Black-backed Gull would be much larger.

Western and Yellow-footed and Kelp and Slaty-backed Gulls would be larger.

California Gull first-cycle birds would be in basic plumage by October and would have developed a pale base of the bill. However, a California Gull still in juvenal plumage could still have an all-black bill. Such a bird however would lack the dark gray and blackish feather on the mantly. Also, I believe that the tertials on juvenal California Gulls are much paler brown than the blackish primaries, matching the brown color of the body feathers.

Resources Used

Sibley Guide to Birds; Grant's Gulls 2nd Ed.

Previous Experience

No previous experience with juv. plumage LBBG, but I have seen a handful of 1st basic birds in Colorado, as well as numerous older birds in Colorado and elsewhere.

Notes

Memory

Additional Information

Comments: Although LBBG has become more common in Colorado, and is no longer a review-list species, the appearance of juvenal-plumaged birds at the early date of October 11 is quite interesting (even if the bird was partially molted to basic plumage) and suggests the possibility of a nearby (e.g. North American) breeding site.
Time: early afternoon (about 2 pm)
Elevation: about 5000
Other Dates:
Nearest Town: Fort Collins
Independent Observers: I am original observer

Date Documentation Submitted

10/16/2005 4:34:00 PM

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Location Map

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