ML629336574

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Midway through a morning studying thousands of gulls at the Magnolia Springs landfill, an unusual near-adult bird was spotted but was partially obscured by debris. Though the primaries were not visible, I felt this robust and large bird appeared unusual and moved closer and to a better angle to see it fully. On doing this I noted the gray coloration of the primaries which brought instant thoughts of Glaucous-winged Gull. I studied it intently over the next hour, obtaining multiple photographs in flight and at rest. After deciding it was indeed highly likely a “pure” GWGU, I called a few local observers for confirmatory observations and opinions; this was done in a conservative approach, given hybrid-related questions encountered with this species, as well as the “messy” appearance of the bird and hints of immaturity. Several observers arrived and saw the bird well, and after discussion of various possibilities we all agreed on Glaucous-winged. This news was then released more widely late that morning, with reports continuing into the afternoon. Conditions of observation: Observed over a three-hour period in excellent full sunlight (sun behind observer) as close as 40 m with Zeiss 10x42s and Questar 64x. Seen in a flock with multiple different individuals of American Herring, Ring-billed, Laughing, and Lesser Black-backed gulls. Noted at rest at all angles and multiple times in flight. Interestingly, this bird often either did not fly, or was the last to fly, when the flock would spook into the air. Multiple photographs were obtained at rest and in flight. Size and structure: Large bird, mildly larger than Herrings. Bill larger than Herrings with strong gonydeal angle; bill yellowish at base, dark in central portion, and reddish distally (likely some soiling from red dirt as well as red gonydeal color). Long sloped forehead, small eye positioned in upper face, robust body, medium wing projection, heavily-built legs. Irides dark. Legs and feet pink, though soiled with red dirt. Likely a male based on structure and size. Feathering: At rest: Head white with moderate streaking on the crown, rear face, and nape. Anterior face with dark smudging, likely soiled from feeding in that environment. Hindneck slightly streaked, becoming less defined and more smudged in appearance inferiorly. Back, scapulars, and secondary coverts gray; tone similar to adult Herring and Ring-billed gulls though minimally darker when compared in photos. Prominent white tertial steps and prominent white secondary skirt visible at rest. Secondary coverts, lower scapulars, and tertials with moderate wear creating a “shaggy” appearance on this bird, with perhaps a hint of brownish on the coverts (could be wear related). Folded primaries at rest essentially concolorous with mantle, only slightly darker distally, with moderate-sized white apical spots. Throat and breast moderately smudgy-brown with subtle horizontal barring giving a partial hooded effect. Remainder of underparts unmarked white. Tail white. In flight: In flight (as observed several times in the field and as seen in photographs) wings were essentially gray and white, and tail all white, without dark markings. Primaries showed a white “string of pearls” effect with thin subterminal crescents. Moderate white apical spots present on primaries, and secondaries showed a broad white trailing edge. Gray of the distalmost portions of the primaries slightly darker than the more proximal portions, but similar in tone to mantle and coverts. Under primaries all pale gray. In photographs there may be a slight amount of brownish tone to the under lesser secondary coverts. Age and molt: Age of this bird is listed as a “near adult” due to mild indications of immaturity, mostly the amount of dark on the bill but possibly also slight brownish tones on secondary coverts. Photographs show what appears to be a molt gap in the inner secondaries, and the tips of p5-p8 show more wear suggesting they might be older than the inner primaries (though this is not obvious on p9 and p10). This raises the question in January of delayed or arrested late stage of prebasic molt. I suspect this is a “retarded” fourth-cycle bird, though possibly an advanced third-cycle. Identification: Identification as a Glaucous-winged Gull by combination of multiple characters of size, structure, soft part color, and feathering. Key points are the size mildly larger than Herrings, large bill with strong gonydeal angle, dark irides, prominent tertial steps and secondary skirts, gray primaries essentially concolorous with mantle, thin “string of pearls,” hooded effect with smudgy, horizontally-oriented breast markings, and pink legs. Hybrids: After study in the field at rest and in flight, discussion with others called to the scene, review of hundreds of my photographs, and examination of the literature, I feel comfortable this bird shows primary markings within the accepted range of “pure” Glaucous-winged, without significant indication of hybrid origin. I feel both Olympic Gull (Glaucous-winged X Western) and Cook Inlet Gull (Glaucous-winged X American Herring) should show darker primaries and are not significant concerns. Nelson’s Gull (Glaucous X [any] Herring Gull) should have a pale iris and darker markings in the primaries with different pattern. Seward’s Gull (Glaucous-winged X Glaucous) should have a paler mantle and paler distal primaries. Glaucous-winged X Slaty-backed should have darker primary markings. Glaucous X Great Black-backed should have darker mantle and wings. No other hybrid combination is thought relevant. Other species: American or European Herring gulls excluded by size/structure, dark iris (for age), gray primary tone and pattern lacking black, and also prominence of secondary skirt/edge and tertial steps. Slaty-backed Gull would show a similar “string of pearls,” but excluded by mantle and primary tone and dark irides (rarely dark in that species for this age). Western Gull and Yellow-footed gulls excluded by mantle tone, the latter also by leg color. Glaucous Gull excluded by primary tone/pattern and iris color. Iceland Gull (including Thayer’s) is smaller than this bird and with much smaller bill, also with different combination of primary pattern/tone. Vega Gull would be slightly darker in mantle tone but would show obvious contrasting black on the primaries. Lesser Black-backed Gull and the Yellow-legged/Caspian complex usually smaller than this bird, with darker mantle, black on primaries, usually yellow irides (except most Caspian), and yellow legs. California Gull smaller with darker mantle, contrasting black in primaries, and yellowish legs. No other species are considered as identification contenders. Experience: I have seen many Glaucous-winged Gulls on the West Coast though not since the early 1990s. I was an observer/photographer of the only prior Alabama bird at nearly the same date (4 January) at this site in 2008. Experienced with many other large gull species and forms from decades of gull study in North America and multiple continents.