14 December 2015

Head Shape in Large White-headed Gulls

Not just large white-headed gulls, but birds in general, will appear to have varying head structure (and body) depending on behavior and "emotions". That's right, emotions. A bird feeding will not look the same as a bird in a relaxed state. A bird alarmed will not look the same as a bird that's preening. Environmental factors also play a role in this subject too: wet feathers, versus fluffed feathers on a windy day can substantially change the bird's appearance.

3rd cycle type Herring Gull. Waukegan, Illinos 12 December 2015.

The image on the left shows a flatter crown, short neck, and higher clearance under the body.
The image on the right has a gentle female-Iceland shaped head that's rounded, neck outstretched, a "Slaty-butt" and what looks like shorter legs (making it look more squat).

Why is this worth mentioning? I've read too many comments recently where people will eliminate a certain taxon based on the shape of its head or body - all this based on one still image. It's important to note that these assessments can only be accurately made in "real life" or video recordings. Relying on still images is risky business, and quite frankly, sloppy. Of course if there's a series of photos, an average can often be ascertained, especially if there are other bids in the frame for comparison.

The center photo in the collage below shows the most accurate shape and structure of this Herring: