The Odd One Out

It is the beginning of November, autumn has only just started and we still have a long winter ahead of us. Here in Europe, adult and fledged gulls have left their breeding grounds roughly around July and have since fanned out in various directions. Some individuals have already traveled hundreds of kilometers to spend the winter far south. Young gulls are supposed to take care of themselves and adults have split with their mates to become individuals again.

In the latter stages of the breeding season, gulls have started their moult to basic (non-breeding) plumage. Distinct colouration of legs, bills, eye rings and hoods — used as signals of good health in order to attract a mate — have since started to fade because their function is not required anymore. Not until the beginning of next year will these colours return and feathers will be replaced during the moult around that same time so that the to alternate (breeding) plumage is acquired once again.

Not so though for all individuals.

Every now and again you come across an individual who is the exception to the rule.

Today I saw the first Black-headed Gull with a strong outline of its brown hood:

Black-headed Gull, adult, early head moult
Adult Black-headed Gull with the outline of the hood clearly visible. Leiden, The Netherlands, 4 November 2011.

Black-headed Gulls at this time of year are supposed to have no hood at all, but instead a white head with two black ear spots and faint bands going across the head, connecting both ear spots and both eyes.

Black-headed Gull, M[Arnhem 3618180]
Adult Black-headed Gull in typical basic (non-breeding) plumage. Leiden, The Netherlands, 30 October 2010.

Those individuals who moult their hood early apparently do so every year. What is interesting though is that their moult takes place over a much longer period of time than for those individuals who acquire their full hood during the regular moult stage. Those who have a normal moult do so very quickly, up to 10 – 15% a day. This means that a full hood can be acquired in around a week. The individuals that I have seen with early head moult (see examples below) took weeks before their hood was anywhere near completion.

I have a feeling that the individual I saw today is the same one that I observed at the same time and at the same location last year. Black-headed Gulls have a tendency to spend the winter at the same location each year, so the odds are in favour that this is the same gull (although it cannot be proven without other distinctive characteristics or a ring around its leg).

The following images are of the individual photographed last year at the same location (Leiden, The Netherlands):

Black-headed Gull, adult
Leiden, The Netherlands, 31 October 2010.
Black-headed Gull, adult
Leiden, The Netherlands, 6 November 2010.
Black-headed Gull, adult
Leiden, The Netherlands, 20 November 2010.

Some more examples:

Black-headed Gull, adult, W[E5RE]
Leiden, The Netherlands, 28 November 2010. See this page for a full set of images of this individual in various plumages.
Black-headed Gull, adult, active head moult and pink body
Leiden, The Netherlands, 30 November 2010.
Black-headed Gulls, one with active head moult to summer plumage
Leiden, The Netherlands, 22 January, 2011.

For more information about head moult in Black-headed Gulls, visit the site of Frank Majoor.

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