Gulls in NW Europe
(last update: September 25, 2011
Herring Gull sub-adult, January 23 2013, Katwijk, the Netherlands.
4CY and 5CY birds difficult to separate in many cases, but a single small mirror on P10, much dark in secondaries & tail, and extensive brown coverts is generally associated with 4cy birds.
Showing tail and upper-wing pattern. Inner primaries without obvious brown to grey cast or arrow pattern near tip (as in 3cy); instead, 4cy birds often have adult-like grey inner primaries with a white tip. Central primaries normally echo the adult pattern, showing obvious sub-terminal bands with pale tip on P5. Outer primaries may appear surprisingly immature, brown without white tips. P10 may or may not show a mirror. At least a reasonable set of secondaries appear adult-like, predominantly grery with an obvious white tip.
Bird below: almost completely white tail with single black streaks, mirror on P9 and P10, not much black on bill indicate 5CY.