Great Black-backed Gull (Larus marinus)

(last update: July 12, 2015)

Great Black-backed Gull 1cy November

Description of 1st winter plumage

First-winter (Sep-Mar) similar to juvenile, but head and upper breast whiter with narrower dark streaks (especially around eye and on hindneck); forehead normally white. May show dark ear-spot. Mantle and scapulars pale grey to buff with blackish subterminal bars or anchor-shaped spots; often intermixed with juvenile feathers. Bill similar to juvenile, but some develop paler base from early winter. Pale individuals have whitish underparts, narrower dark subterminal marks on upperparts and narrow dark covert-markings. With wear may bleach as described under Herring Gull, but rarely as extreme (an extremely pale spring bird shown by Grant (1989a) could to my eyes be partly leucistic, as the upperparts appear unmarked, which is atypical even in very worn birds). (Malling Olsen, K. & Larsson, H. 2004 Gulls of Europe, Asia and North America. London: Christopher Helm).

Moult into first winter

Juvenile moult to first winter plumage partial Aug-Nov, including mantle, scapulars, and (probably) parts of head and body. Often no sign of moult into Nov/Dec. (Malling Olsen, K. & Larsson, H. 2004 Gulls of Europe, Asia and North America. London: Christopher Helm).

Although Malling Olssen states "often no sign of moult into Nov/Dec", this is not supported by data of ringed birds. The table presented in September illustrates that already 40% (n = 10) do show the first signs of moult, i.e. new upper scapulars. By November, over 90% (n = 45) replace the upper scapulars and 75% has started moult in the lower scapulars as well.

By November, all ringed birds (except for 3EN blue from Ireland) had at least some new upper scapulars, with the majority of birds categorised ">75% of the upper scpaulars replaced". There may be a bias towards southern populations, as many images on this site are from birds ringed in S Norway or colonies further south like Denmark and France. It remains pure speculation, but it would be interesting to know where very fresh juvenile birds in November, like THIS ONE hatched. Birds similar to this one, but still fresh by 2cy March, are represented by THIS POWERFULL bird, which is believed to have travelled from far northern Europe. A far northern hatching colony does not necessarily reflect late moult in scapulars. In February we photographed this Russian bird from Murmansk, with quite average moult scores in the scapulars.

All wing-coverts, tertials and flight feathers still juvenile by October. By November, one single bird (J17Y) that had gc2 missing.

top: marinus 1cy JJ77 November 25 2006, Boulogne/Mer, N France. Picture: Mars Muusse. Within the sample of ringed birds on this site, this is the most 'retarded' bird' for November, with only single upper scapulars replaced. Class: US=1-25%, LS=0%, TOT SCAPS=1-25% .

below: marinus 1cy JP568 November 15 2012, Boulogne-sur-Mer, NW France. Picture: Jean-Michel Sauvage. Example bird for several individuals that have almost all scapulars replaced for 2nd gen feathers. As a rule, the rear feathers in the lowest row of scapulars are the last juvenile feathers in the scapular region. Class: US=100%, LS=75-99%, TOT SCAPS=75-99% .

Tables:

below: graph corresponding to data from table 1. n=54. Distribution of replaced 2nd generation scapulars in November 1cy GBBG, separated into Upper Scapulars, Lower scapulars and for Total scapular region. Classification in 6 classes, running from 0% (no 2nd gen scaps) to 100% (all scaps in a region have been replaced).

It is clear from the column "Total scapulars" that less than 10% of the ringed November birds scored "0% 2nd gen scaps" (in fact, only 1 out of 45 ringed birds was still in completely juvenile plumage), in other words, the other 90+% of those 45 ringed birds had replaced at least one or more (upper) scapulars for 2nd gen feathers.

below: Great Black-backed Gull JA804 illustrates differences in colour and pattern between old juvenile 1st generation scapulars and fresh buffish 2nd generation feathers. Bird ringed as pullus on June 12 2012 at Salvøy, Karmøy, Rogaland, Norway (59°17'54"N 005°12'27"E). Picture: Jean-Michel Sauvage, September 28 2012, Boulogne-sur-Mer, NW France.

below: Distribution of replaced scapulars for "Total scapular region" for months August in hatch year until commencement of first complete moult in April. Classification in 6 classes, running from 0% (no 2nd gen scaps) to 100% (all scaps, including long rear scaps, have been replaced). Only ringed birds, n=238.