glaucoides - kumlieni

(last update: January 26, 2012)

Iceland Gull 1st cycle (2CY) January 23 2013, Quidi Vidi Lake, St. John's, Newfoundland. Picture: Jan Baert.

Age 2cy: showing dark bill.

Wing-tip pattern is a plain brown wash over the centre of the outer primaries and extending almost to the feather tips. The outer 5 primaries show dark oute- webs and pale inner-webs. These dark outer primaries contrast with less well marked, paler inner primaries. In this pattern it recalls 1st cycle (juvenile primaries in) thayeri.
In typical glaucoides, the very tip of the outer-webs are white, with obvious chevrons or ´arrow/head patterns´ on the central and inner primaries. Also, there is extensive spotting just above the chevrons, continuing to halfway the feathers in P1-P3, and less extensive central primaries, but even still obvious on P6. This pattern is copied on the tips of the greater primary coverts, and worth checking, as patterns on exposed primary tips can easily bleach and wear away (making exact valuation of original patterns difficult), while the primary coverts are often hidden in resting birds so patterns are better conserved.

This bird has a plain tail pattern (single internal markings), the tail-bar contrasts with paler, dark-barred uppertail-coverts. A dark tail-bar is present in 15% glaucoides, in 80-95% kumlieni (Zimmer 1991). The tail-bar of kumlieni is often rather uniform, just with faint pale (often broken) mottling at tip of tail and along edges of T1-T2, whereas tail-bar of glaucoides typically consists of narrow bars melting together. Thayer’s usually has darker, mud-brown tail-bar with pale mottling restricted to base and edges of rectrices.

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