Common Gull Larus canus canus & L.c. heinei

(last update: March 12, 2012)

Common Gull (Larus canus) 2cy January - March

description

(P.J. Grant: "Gulls, a guide to identification")

Common Gull has a partial moult in spring. It starts in February and is completed by April, leaving birds in so-called "first summer" plumage. The head turns much whiter, with the white chin, throat and breast white and dark streaking confined on the crown, hind-neck. The tertials, wing-coverts, primaries and tail-feathers are excluded from this moult and turn paler, the grey parts turn almost white and very worn at the tips. The dark primaries and the lesser coverts start to bleach to pale brown. The second generation grey scapulars create a saddle. The legs are greyish.

From June to October, a complete moult will bring birds in so-called "second winter" plumage. The head and hind-neck are strongly spotted and from the hind-neck, these spots form streaks, creating a collar running down the sides of the breast. Under-parts, tail-coverts and rump are white. The second generation primaries resemble adult primaries, but the black is more extensive in the outer-wing, with black sub-terminal markings down to P4 or even to P3. The greater and median primary coverts and the lesser coverts in the carpal edge are dark centred as well. The white tips on the outer primaries are ill-defined, wearing off quickly and the mirrors on P9 and P10 are smaller than in full adult plumage. The tail is all-white in race canus. The iris is brown, the greyish bill has a clear black bill-band. 
After the complete moult in June to October, brachyrhynchus may still show several immature feathers in the wing. The central tertials and some of the tail-feathers may show dark immature centres (even creating some kind of a tail-band in some individuals). Immature features can also be found in the central greater coverts and in the carpal edge and can even be found on the upper-tail and under-tail coverts. These immature features are less often found in nominate canus, which show no vestiges of a tail-band from autumn 2cy onwards ("second winter" plumage and later). In this respect, brachyrhychus resembles Ring-billed Gull, L. delawarensis. From autumn 2cy onwards, the iris in brachyrhynchus may turn obvious pale.
The race kamtschatschensis shows similar amount of patterning after the complete moult as brachyrhynchus, with many immature markings in tail, tertials and wing-coverts. Moreover, (all?) kamtschatschensis still shows black tips on the white under-wing coverts. 

1st winter heinei

from: Gulls of Europe, Asia and North America by: Klaus Malling Olsen & Hans Larsson.

GEOGRAPHICAL VARIATION Three taxa.
L. c. canus (NW Europe to Baltic and coast of Russia east to Moscow and Kola Peninsula. Winters N, W and S Europe). Wings on average shortest in S part of breeding range (see Measurements).
L. c. heinei (Russia E of range of canus; from E of Moscow and between Kanin Peninsula and basin of Lena River; occurrence further E poorly established (Dement’ev & Gladkov 1969). Winters Baltic to Black Sea and NW Europe, rarer Persian Gulf to Pakistan; recorded on migration E Asia and rarely in winter in Korea and Hong Kong (G.J. Carey in litt)) Very similar to canus. lntergrades common in W Russia, including both wing/tarsus length and plumage characters, making field identification impossible in all but large birds. Combination of heinei measurements and canus plumage characters typical in Estonian breeders; many wintering birds from the Baltic have canus measurements combined with heinei plumage characters (Johansen 1961, Carey & Kennerley 1996, Bengtsson & Pedersen 1998, pers. obs., skins in UZM, ZMA). Ringing recoveries of Danish and Dutch winter birds from breeding areas of heinei (Russia, Kazakhstan (K. T. Pedersen in litt.) confirms occurrence in W Europe. Only birds showing a combination of heinei measurements and plumage characters are included in the summary below and measurement series.
L. c. heinei often has a fuller head (and thus sometimes a smaller-looking bill) than canus. Has 'hanging hand' habit (as in Iceland Gull) as a result of longer wings. On folded wing, tertials cover three (four) inner primaries (four in canus). Compared to canus, wing-tip generally more pointed: P10 (0)4-10mm longer than P9 (0-7mm longer in canus). Bill generally heavier and more parallel-edged. In the hand, males can be separated on a humerus length of 98.5 or more, ulna length of 112 or more and radius length of 198.5 or more, with females 95.5, 107 and 104 respectively (Kompanje & Post 1993). Measurements in adult January section.

Head and underparts generally heavier marked in winter/first-years, sometimes forming complete dark-spotted necklace or large dark patch around eye (rare in canus). Rump and tail-base with heavy dark markings.
First-winter similar to canus, but greater upperwing-coverts on average darker, deeper brownish-tinged, typically with weak dark subterminal spots; outer greater coverts gradually darker; sometimes similar to first-year Lesser Black-backed. Greater coverts may, however, be paler, offset by better wing contrast: lesser coverts generally darker brown than in canus, creating a stronger dark leading edge to the inner wing. Underwing similar to canus, but often paler with narrower, more distinct dark edges to coverts and axillaries; some with barred axillaries as in Eurasian Curlew Numenius arquata, others white (underwing then resembling first-year Ring-billed Gull). Dark tail-bar similar to canus (40-51mm on T1 ). May develop pale bill-tip from May, earlier than canus.
Second-winter more often than canus has dark markings on lesser coverts, secondaries and tail (in about 10%; dark tail markings in 25% of Common Gulls in Finland, winter (Peltomaki 2000) suggests heinei). Size, wing-tip pattern and more heavily marked head and body in winter plumage invites confusion with Ring-billed Gull, but as dark as or darker than canus (Ring-billed paler than canus).
Moult generally later than in canus. Most adults still show winter head in mid-Apr, when S Scandinavian breeders are white-headed (pers. obs,). P1-P2 late June.
Moult to first-winter on average later (Aug-Nov); in late Sep no sign of moult to first-winter (Skjapin 1977, Tove 1993). Most Oct-Dec birds show <50% new mantle feathers (all or most of mantle normally renewed in southern canus; moult of N canus similar (Bengtsson & Pedersen 1998). Most Finnish winter birds (showing heinei characters) retain >50% juvenile mantle late Dec.
Primary moult probably slightly later than canus.

Larus canus heinei 2cy - on measurements or location

Larus canus canus 2cy - on location