Great Black-backed Gull (Larus marinus)

(last update: July 12, 2015)

Great Black-backed Gull 1cy December

top: marinus 1cy, December 15 2012, IJmuiden, The Netherlands. Picture: Mars Muusse. Classic tail-pattern with much proximal white on the outer rectrices and the sub-terminal band hardly reaching the outer-web of R6. Pale inner primaries and pale 'lozenges' on th eouter-webs of P1-P4, the prominence of the pale window depends on the relative angle of the wing.

below: marinus 1cy, December 15 2012, IJmuiden, The Netherlands. Picture: Mars Muusse. Some individuals have rather dark inner primaries, lacking an obvious pale window, especially when the wing is half-folded.

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.

Despite its southern hatching location, this 1cy bird black JJ77, showed only very limited scapular moult by December, and from all 8 ringed birds in December, it was obviously most retarded.

top: marinus 2cy, February 02 2012, IJmuiden, The Netherlands. Picture: Mars Muusse. February, and still the vast majority of scpaulars juvenile, only single upper scapulars replaced. In W Europe, we may have northern Herring Gull argentatus and northern Great Black-backed Gull marinus from mid-October onwards. Their origins are N Norway (up to 70" N) and Russian White Sea (65" N), and we think those are the locations where these 'retarded moulting' juveniles come from. There are several birds on this site that have the fringes of the juvenile scapulars even in better condition than this bird above, even in late winte (February).

below: marinus 2cy RUM ES008270, February 01 2011, Scheveningen, the Netherlands. Picture: Mars Muusse. Bird from N Russia (68°46'59 N, 37°25'0E). Despite the northern origin, almost all scapulars replaced.

below: marinus 2cy JA911 February 27 2009, Fraserburgh, Scotland. Picture: Mars Muusse. You won't get them from much further north in Europe, hatched Hornøya, Vardø, Finnmark, Norway (70°23'16"N 031°09'21"E). Most upper scapulars replaced by late February.

Tables:

below: graph corresponding to data from table 1. n=23. Distribution of replaced scapulars in December 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 December birds scored "0% 2nd gen scaps" (only 1 out of 22 ringed birds was still in completely juvenile plumage), in other words, the other 90+% of those 22 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.

ring projects Norway & Denmark:

ring project Germany:

ring project France:

ring project Ireland:

ring projects Appledore Island, US:

unringed birds: