Dead Bird Quiz answers

17 11 2011

Juvenile Great Black-backed Gull. Photo by D. Minsky.

Two responses on this quiz: John Stanton and Dennis Minsky buzzed in with answers, and for Bird A, their differing responses perfectly illustrate the challenges of identifying dead gulls. Bird A is, in fact, a young Great Black-backed Gull similar to the one shown here. Juvenile GBBGs have a bold, black and white checkered pattern all over their backs and wings, which sets them apart from young Herring Gulls, which are a more blended gray overall. But John brought up the possibility that Bird A might be a juvenile Ring-billed Gull. In the picture here of a living specimen of a RBGU, you can see the similarities. While RBGU show a much greater degree of variation in their juvenile plumage, it is possible to find individuals with patterns similar to that of a GBBG. This drives home the importance of scale. I did not provide measurements for Bird A, but its wing chord was 47cm. This is massively longer than the RBGU, whose wing chord maxes out at 38cm. This is, clearly, an object lesson in taking measurements on all your carcasses–it can make the difference between “very confident” and “dunno” in our database.

Juvenile Ring-billed Gull

Bird B was unanimously and correctly identified as a young Laughing Gull. In comparison with GBBGs and RBGUs, young LAGUs show a darker, slaty back with dark brown feathers interspersed, and no white checkering anything like the other two species. We expect to get many more reports of Laughing Gulls from our new North Carolina contingent as winter sets in since this species tends not to hang out much here in New England in the colder months. They may be on to something…

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