Black-headed Gulls with gray hind neck

[little-W]

I came across a few BHGs today (in a group of about 60), that showed distinctive gray on the hind neck, sides of the neck and throat, and on the head.
Any thoughts are welcome.

Pictures taken in Leiden, The Netherlands.


Black-headed Gull, gray neck and head by little-W, on Flickr


Black-headed Gull, gray neck and throat by little-W, on Flickr


Black-headed Gull, gray neck and throat by little-W, on Flickr

[Rob Hoeben]

Hi Maarten,

Somehow I did not note the gray before, but going through my pics I found one BHG with a very similar pattern. It is clearly visible on photographs made on Dec 22, 2009 In Leiderdorp, The Netherlands. The gray pattern is retained for a year as it is still visible on photos made on Dec 5, 2010 at the same spot. The bird was ringed with Hiddensee IA114104 as an adult male on May 19, 2008 in Mecklenburg-Vorpommern, Germany (53°57'N 014°02'E).

Rob

[Klaas van Dijk]

It is not uncommon for an adult Black-headed Gull in non-breeding plumage to have two of these bands. See e.g. http://frankmajoor.nl/PDF/Kokmeeuwen-Go ... aar-95.pdf for more information on the individual variation in the non-breeding plumage of adult Black-headed Gulls (page 152 and 153, in Dutch).

Klaas

[little-W]

Rob, thanks for pointing out this individual, especially the 2009 photos. Needless to say that we didn't spot the coloration when we were observing that gull on Sunday together.

Looking through my own photo collection and at individuals in the field today and last Sunday, I do now see that some individuals have a gray hind neck whereas others don't. However, I haven't seen any individuals with the extensive gray areas to the sides of the neck.

I now think that the lighting conditions have a lot to do with it as well. At the time the photos were taken, it had just stopped snowing heavily and the light was very diffuse due to the thick snow clouds. The effect seems to be much less in brighter lighting conditions.

Still, it's quite an interesting coloration. I also checked with Frank Majoor but he didn't have an explanation for it either.

@Klaas: the discussion is not about the head pattern, but the gray coloration that we noticed extending from the neck