This is the third of today’s five different Caspian Gulls at Lakolk on Rømø where four were photo documented and the other three to be seen here, here and here.
Characters in favor of cachinnans are the relative long thin bill without pronounced gonys angle and a black spot above the red gonys area, the relative small and darkish eye in a pure snowy white head, the slightly darker upperparts than on nearby argentatus and the good cachinnans jizz with a push up breast, small head, flat back and slender elongated rear with long primary projection. Additionally the small white apical spots are good for cachinnans as is the all white tip of p10. 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 colour is typical blood red in michahellis and light pink in argentatus.
Seen on location but without documentation was pale yellowish and relative long thin legs (seen when the bird was standing), broad black band on p5 and classic grey tongues on outer primaries surrounded by a black cachinnans boomerang (created by the black primary markings seen from underneath when flying off).