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. Wing-tip pattern is a plain grey-brown wash over the centre of the outer primaries and extending almost to the feather tips. The outer 6 primaries show dark outer-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.

Such dark primaries with a smooth texture, lacking chevrons and spotting near the tips is probably not possible in glaucoides.

This bird has an indistinct 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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