Sunday, 14 December 2008

Caspian Gull (Larus cachinnans), ad, 13.12.2008, Lakolk Strand, Rømø

This Caspian Gull has relative long and characteristic pale yellowish legs. Most often when seeing cachinnans their thinner legs and longer tibia compared to argentatus is quite distinctive.

In frontal view the small dark eye of cachinnans looks as if it has been squeezed into the head due to the more “inflated” surrounding areas with broader and bulbous cheeks, loral patch and eyebrows, and enhanced by the slim bill. The small eye is situated more frontal because of the flatter forehead than in argentatus and the eye colour is relative dark with a slight green peppering in the iris – most easily seen when light hits the eye directly - and when seen at some distance it stands out as being dark in contrast to argentatus. There is a thin red orbital ring seen at close range.

The bill is relative long and without pronounced gonys angle. On the yawning gull the bare part colour in the opened bill is spot on cachinnans being orangey-yellow at the base of the mandibles where the skin colour in michahellis is typical blood red and light pink in argentatus.

It has a good cachinnans jizz with high push up breast, flat belly slightly dropped behind legs and long slim elongated rear. Additionally the upperparts are slightly darker than nearby argentatus which was obvious in both overcast and sunny weather.

It is not yet in full summer plumage as it has retained some of the dark spotted neck boa in contrast to the snowy white unspotted head. The distinctive black feather shafts on the outer primaries in the upperwing is commonly seen in adult cachinnans and in the stretched wing the grey tongues on the outer primaries are obvious when seen from underneath and even from above on one photo, on p5 there is a broad black band, on p10 the outer tip is all white. The white apical spots are all relative small. In flight the hand is slender and when seen from the underwing the black on primaries creates a classic cachinnans boomerang.

No comments: