530 Peregrine Circle,
Species, Date, Time and Location Information
Duration (total time in view):
45 seconds or so
N Weld County Landfill
Description of the Bird
On 17 November 2011, I was standing on the road just s. of the N. Weld County Dump. During fall 2011, work at the dump has been along its south side and thus facing towards, and closest to, the road -- optimal for observing the gulls feeding there. At about 10:15, under high overcast skies (sun would have been mostly to my back), nearly all the gulls took to the air. I noticed a small gull (i.e., compared with California/Herring/Thayer’s) with an all medium-brown tail contrasting with a whitish rump heavily bared in brown. As these features are not those of a Ring-billed Gull, I focused my attention on that bird. Its wing pattern was not nearly as contrasting as that of that of a first-cycle Ring-billed Gull. I watched the bird carefully as it circled a few times, and it was also clearly smaller than the RB Gulls around it. This combination of features led me to call out Mew Gull. David Leatherman tried to locate the bird but couldn’t do so before the swarm settled down, with the Mew landing behind a pile of dirt.
Overall, this was a gull that, in flight, appeared similar in shape to a Ring-billed Gull but was smaller than the 50+ Ring-billeds that I could easily compare it to, including other first-cycle birds. The Mew Gull’s head and body seemed rather uniform in color, though I didn’t carefully note the back color. I did pay special attention to the underparts (realizing their importance in separating young Mew Gulls from Ring-billeds), and the underparts were uniformly muddy brown down to at least the vent, not largely whitish, or speckled brown, as first-cycle Ring-billed Gulls appear. The tail and uppertail covert pattern were as described above.
The outer primaries were medium brown (not blackish-brown, as on a Ring-billed Gull), and the primary color transitioned into medium gray on the inner primaries. The contrast between inner and outer primaries was not as sharp or stark as seen on a Ring-billed Gull. This could be seen in direct comparison with a first-cycle Ring-billed Gull that was flying next to the Mew Gull. The secondaries were similar in color to the primaries. The greater secondary coverts were similar in color to the inner primaries, and the remainder of the secondary coverts were browner and slightly darker than the greater secondary coverts. I noted little of the back (other than it was not dramatically patterned) or the head (other than it did not dramatically contrast with the body, such as being all white). The bill was not noted either. The underwing pattern was not noted.
Those marks that I mention above were scrutinized several times. The other parts of the body only casually observed as I was focusing on those several key features. The length of observation was about 45 seconds. The distance was greater than 100 meters, and I was using Swarovski EL 10x42 bins with excellent lighting (high overcast, sun would have been mostly to my back. No glare. No heat waves). The wings looked very much like that of the Mew Gull in Howell’s gull book, p. 131, plate 22A.23. The tail and rump looked very much like that of the bird in the attached photo, which was taken in Everett, WA during October (or like that of the Mew Gull in plate 22A.21 in Howell’s book). The wings were rather similar to the Everett bird’s wing as well, but the greater secondary coverts definitely had a grayish hue (like the inner primaries), as seen in the aforementioned photo in Howell’s book.
Behaviors: As above
Call: not heard
Plumage: 1st cycle
Similar Species Discussion
Ring-billed Gull has a narrower blacker tail band, more contrasting wing pattern, particularly outer vs inner primaries, and is not evenly brown colored below.
None, though for comparison, used Howell's gull book and my own photos
Extensive, having seen tens-of-thousands of both species during the last decade
Notes made DURING observation
Date Documentation Submitted
12/3/2011 4:10:00 PM
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