onsdag 22. august 2012

Juv-1w caspian gull Fredrikstad

This nice caspian gull in almost full juvenile plumage suddenly appeared before me at Øra, Fredrikstad in the afternoon of monday 20th of august. I have been searching for one for years, so this was nice...

While first winter caspians are very contrasting and therefore easy to discover and straight forward to identify, juveniles are much more nondescript and requires a bit more attention to build and proportions. Roughly speaking, you take a herring gull and stretch and pull all extremities hard in all directions to get the caspian build. They are slimmer, longer winged, longer legged, longer billed and longer necked than an average herring gull, and it takes a very special herring gull indeed (probably in very bad health) to match one.

This bird is not entirely juvenile, though. It has renewed quite a few mantle feathers and scapulars, but these are rather diffusely patterned and do not contrast very much with the older, juvenile feathers.

I have added almost every photo (albeit of variable quality) I managed to get of the bird...Click for (slightly) larger version.

Rather similar to a juv lesser black backed gull, but upper parts with more of a cinnamon  colour than LBBGs which are usually more chocolate brown.

Note the long wings with very narrow and pointed primaries, on swimming birds reminiscent of a pair of scissors. See also flight shots.
 With two very different juv great black backed gulls...
 Almost like a big-nosed phalarope when swimming on the water...

Long legs and very slender body, pear shaped head, long slender bill. On average much lighter underwings than herring gulls as can be noted in this picture.
Wing bar created by darker bases to greater coverts, inner primaries with light restricted to inner webs creating venetian blind effect and much less obvious primary window than herring.

 Lighter underwing than most herrings, but this individual is not extreme in this respect.

 On last three pics: note again venetian blind effect and wing bar.

 Next four pictures: Very typical slender body and "thumbnails "tertial markings

 At rest a  bit more squarish head shape.

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