April 2023 Quiz

 

September. Michigan.

Age: Pointed primary tips, barred upper tail coverts and an overall uniform dark brownish-black plumage points to a 1st cycle large gull.

Identification: There are several important features to hone in on when looking at an open wing of a 1st cycle large gull: The inner primary pattern, the tail pattern and the greater coverts. Here we see dark inner primaries with very little contrast (as found in California Gull and Lesser Black-backed Gull). The dark tail is found in a number of species, but note the uppertail coverts have a noticeable white base color (not brownish). The outer greater coverts are largely dark, and the upperparts have prominent pale edging. All of these features, when combined, are consistent with the aforementioned, juvenile California and Lesser Black-backed Gull, and this image alone would likely yield and inconclusive identification without more context. Here is the perched bird next to 1st cycle American Herring Gull. 

Given the location, plain and dark tertials with prominent pale edging, and all black bill, it is quite evident this is a juvenile Lesser Black-backed Gull.