Mew Gull Larus canus canus; heinei; kamtschatschensis; brachyrhynchus

(last update: March 12, 2012)

Mew Gull canus SVS 7147797 2cy, 29 November 1997, Malmö, Sweden.

Figure 17: 7147797 (371/95,4) advanced two-year old male (2CY), probable canus, with white tips on P7-P10. 29 November 1997.

The pattern of P8 may serve as a good character to separate advanced two-year old birds from retarded three-year old birds, but advanced birds may look like the one in fig 17 below. This well-developed bird has obvious white tips on P7, P8 and P9 (it proved to be the only bird with a white tip on P9, out of 91 controlled second-year birds). In general plumage this bird very much resembles a retarded three-year old bird and it would not have been aged correctly if it wasn’t ringed in its first year. It even shows a mirror on P10 that merges with the white tip (a character only starting to become common in seven years old birds, according to our material). However, the bird has seven primaries with black and the mirror on P9 is not fully developed.

Retarded three-year old birds may be separated from advanced second-year mainly on the white tip on P8 and normally the mirror on P9 is fully developed. However, some second-year birds (3,3%) have a white tip on P8 (see fig 17 below) and some third-years do not show a white tip or have a very small one (two birds out of 18 in our data set). The third-year bird in fig 19 lacks a white tip on P8, has a dark alula and small dark markings on wing-coverts. The same bird has been documented as four-year old (fig 24) and even in this plumage it still lacks the white tip on P8 and shows the dark alula.

A mature bird in which the mirror on P10 merges with the white tip (broken black sub-terminal band on P10) is shown in fig 27. This P10 pattern becomes more common on older birds, usually from about seven-year old plumage, but sometimes seen in younger birds (e.g. the second-year bird in fig 17 below).

Figure from:
Is it possible to age subadult Mew Gulls Larus canus?
by: Kenneth Bengtsson & Lennarth Blomquist, publication in: Anser 2-42(2003): p 73-92.