glaucoides - kumlieni

(last update: January 26, 2012)

Table 2: Wingtip pattern variation of adult Kumlien’s Gulls in Newfoundland (N = 345 birds).

From: Identification and Variation of Winter Adult Kumlien’s Gulls, by Steve N.G. Howell & Bruce Mactavish, IN: Alula 1/2003.

See also chart for explanantion of stages and classification criteria.

Primary pattern variation can be envisioned by starting with an unmarked wingtip (Stage 0; Plate 2, a) and building upon this (Plate 2).
Stage 1 (9% of N = 345 birds; bird A, bird B) is darker grey stripes on the basal to medial portions of the outer webs of one to four of P7-P10, but with no trace of dark subterminal bands (Plate 2, b-e); note the darker stripes can be difficult to see in the field.
Stage 2 (11%) is darker grey stripes on the outer webs of three to four of the outermost four primaries (i.e. P8-P10 or P7-P10) with partial to incomplete subterminal bands on one to three primaries among P7-P9 (Plate 2, d-f; bird C, bird D).
Stage 3 (12%) is darker grey or more extensive grey on the outer webs of the outermost four primaries plus complete (mostly narrow) subterminal bands on one to three primaries among P7-P9 (Plate 2, g-i; bird E, bird F); only 12% of Stage 3 birds had complete subterminal bands on all three primaries, and the subterminal band was narrow on all 44% of Stage 3 birds with a complete band on only one primary.

The commonest pattern (and that of the type specimen of Kumlien’s Gull) was Stage 4 (55%): darker grey or more extensive grey markings on the outer five primaries (P6-P10) with complete subterminal bands on zero to three feathers among P6-P9 (most commonly on two to three primaries; Plate 2, j-m). This was also the pattern considered typical of Kumlien’s Gull by Grant (1986). Only 4% of Stage 4 birds had no complete subterminal bands, 12% had complete subterminal bands on only one primary (95% on P8; Photo 15), 44% (and the type specimen) had complete subterminal bands on two feathers (88% on P7-P8) and 39% had complete subterminal bands on three feathers (97% on P7-P9).

More extensively patterned wingtips were uncommon.
Stage 5 (4%) is darker grey or more extensive grey markings on the outermost five primaries (P6-P10) with complete subterminal bands on P6-P9 (three to four primaries with wide bands; Plate 2, n, p).
Stage 6 (5%) is darker grey or more extensive grey markings on the outer six primaries, with complete subterminal bands on three to four feathers among P6-P9 (two to four primaries with wide bands; Plate 2, o, q; Bird G).

Of 345 birds, only 14 (4%) had no visible darkening on the outer webs of the outer primaries (Stage 0 = "white-winged"), although seeing darker markings in the field can be virtually impossible (see Bird H, Bird I, Bird J, Bird K, Bird L). The overall appearance (structure, dorsal tone, etc.) of such birds may be typical of other Kumlien’s Gulls, as in this Newfoundland research. Six of these 14 had unmarked pale eyes like Iceland Gull (score of 3); one had an eye score of 1.5 and seven had an eye score of 2.5. If the pale-eyed and white-winged birds were Iceland Gulls they made up only 1-2% of the Newfoundland wintering population.