01 October 2015

September 2015 Quiz


Age: This gull is undergoing its 2nd prebasic molt. The 9th primary is about halfway grown out, while the tip to the 10th primary is barely peeking out next to the greater primary coverts. About half of the secondaries (outers) have grown out and the other half (inners) are dropped.

The upperwing is dark and solidly filled. At first glance one might consider a 2nd cycle Lesser Black-acked Gull or even 2nd cycle California Gull, but there are a few problems for those species.

The tail band is wide (especially along the outer tail feathers) and this isn't very typical in LBBG. The pink-based bill is okay for a California Gull but it would be unusual for a Lesser molting into 2nd basic, particularly the sharply demarcated black tip. The inner primaries are a silvery gray and show strong contrast with the rest of the wing (often found in Herrings). Both California and Lesser Black-backeds show less contrasty inner primaries. Zooming in, one can see new pale gray mantle feathers right down the center of the back. This contradicts a black-backed species and rules out LBBG.

Our quiz bird is a 2nd cycle Herring Gull. The take-away here is that 2nd cycle Herrings can have really dark upperparts in their 2nd plumage cycle. In the summer months some can have very dark plumage aspects. The resemblance to a 2nd cycle Lesser Black-backed is only superficial, though.

Here's a 2nd cycle Lesser Black-backed in a similar molt state for comparison:


Notice how the inner primaries don't contrast with the rest of the wing as much as the quiz bird. The gray on the scapulars/mantle is more of a slaty-charcoal color and not pale gray. Most of the bill is still black, although it could be partly black and partly pale in LBBGs at this age.