768 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



exposed portions of primaries, inner secondaries and some wing- 

 coverts faded to white. 



Fifth winter. — Apparently like adult but probably some forward 

 individuals become like adult in fourth winter. 



Measurements and structure. — $ wing 450-490 mm. (juv. 450- 

 470), tail 170-195, tarsus 70-75, bill from feathers 60-70 (juv. 55- 

 63) (12 measured). $ wing 440-480 (juv. 435-445), bill 53-61 (juv. 

 52-57). Primaries : 1st narrow, pointed and about two-thirds 

 primary-coverts, 2nd longest, 3rd usually as long but sometimes 

 5 mm. shorter, 4th 10-25 shorter, 5th 35-45 shorter. Rest of 

 structure as in Herring-Gull. 



Soft parts. — Adult and 1st winter as in Herring-Gull and 

 apparently other stages as in that species, but orbital ring in adult 

 vermilion. 



Characters. — No subspecies recognized. Large size and deeper 

 bill distinguish it from Iceland Gull, and absence of black at tips 

 and white or whitish shafts of primaries at all ages from other 

 British Gulls. 



Field -characters. — Adults can hardly be confused with any bird 

 except Iceland Gull, which they closely resemble except in size, 

 being considerably larger. Size equal to L. marinus, but Glaucous 

 has pearl-grey mantle and white primaries. Immature birds can 

 generally be distinguished by large size and brownish markings, 

 but white primaries. Rather silent as a rule, but has a variety of 

 wailing notes, not unlike those of Herring-Gull. (F. C.R.J.) 



Breeding-habits. — Social in its breeding-habits ; sometimes a 

 few pairs nesting together, but occasionally in good sized colonies. 

 Nest. — Usually bulky where material is available, but sometimes 

 quite scanty, generally built of clumps of moss, with admixture of 

 plants (Cochlearia, etc.), also at times seaweed only and generally 

 placed on slopes of cliffs above colonies of rock-breeders, but also 

 on low shingly islands, on sandy islets, occasionally at foot of cliffs 

 or on pinnacles and stacks. Eggs. — Normally 2-3 but 4 have been 

 recorded, ground-colour ranging from stone-colour to umber-brown, 

 occasionally pale bluish-green or rarely reddish-brown, blotched, 

 spotted or streaked with dark umber and ashy. Average of 115 

 Spitsbergen eggs, 76.81x53.98. Max. : 89x60.9 and 79.6x63.2. 

 Mn. : 69x56.1 and 75.5x50.8 mm. Breeding -season. — From end 

 May to mid-June in Spitsbergen, but late layings may be found till 

 July. Incubation. — Doubtful whether male takes part. Period 27-28 

 days (Swenander). Single brooded. 



Food. — Carrion (dead whales, blubber, reindeer, walrus, bear, etc.), 

 birds (Little Auk, Kittiwake, Guillemot, young Ivory-Gull, wounded 

 Ducks, Coot, etc.), also great numbers of eggs and young of Brun- 

 nich's Guillemot ; droppings of large mammals (Polar bear and 

 seal), fish (alive and stranded), Crustacea (chiefly crabs), amphipoda, 

 star-fish, echini, mollusca, garbage of all kinds, algae (chiefly Alaria 

 esculenta), and berries of Empetrum nigrum. 



