THE BLACK -HEADED GULL. 737 



has usually longer bill (^ 36-40, $ 31-38), but is otherwise as L. r* 

 ridibundus and not very well defined. Dark brown head of adult 

 summer, slender bill, black on inner edge of primaries and white 

 coverts along edge and bend of wing distinguish Black-headed 

 from other British Gulls. 



Field -characters. — Carmine bill and feet (yellowish -red in 

 immature bird), and, in breeding-season deep chocolate-brown hood 

 distinguish it from all commoner Gulls. Smaller than Common 

 Gull or Kittiwake, of more slender build and buoyant Tern-like 

 flight. Juvenile, unlike Common Gull, is white below and has 

 patch of dark grey on ear-coverts as has adult in winter. At all 

 ages broad white margin to front edge of narrow, black-tipped wing 

 is diagnostic in flight. More frequent inland than any other Gull, 

 not only in nesting season but throughout year. Cry a querulous 

 scream " kree-ah." In the babel at nesting places most prominent 

 sound is a sharp " kik, kik, kik " followed by loud hoarse " quarrr " 

 as bird dashes at the intruder and then swerves upwards. 



Breeding-habits. — Breeds in colonies, often of vast extent, in 

 very varied sites : among sandhills by the sea, on islands in lochs 

 and meres, in shallow water among growing vegetation, on shingle 

 and low sandbanks frequently near sea, but also at times far inland. 

 Exceptionally has nested on sheds and other buildings and on low 

 trees. Nest. — Carelessly built of any available vegetable matter at 

 hand, size varying accordingly. Eggs. — Xormally 3, but 2 not un- 

 common and 4 occasional. Ground-colour normally from light 

 bumsh-stone to deep umber -brown, spotted and blotched with 

 dark blackish-brown and purplish shellmarks, but in large colonies, 

 and especially where eggs are freely taken, eggs with blue ground, 

 with or without markings, also occur, and a red type has been 

 rarely recorded. Average of 100 British eggs, 51.94x37.19. Max. : 

 58x36.2 and 53.8x39.3. Min. : 46x38.3 and 49.7x34.4 mm. 

 Breeding-season. — From last week April onward. Incubation. — By 

 both sexes. Period apparently variable ; usually 23-24 days, but 

 by some observers stated to be 20 days (Gladstone) and 17-18 

 (Bahr), but last seems much too low an estimate. Single brooded. 



Food. — Largely worms and insects, especially in breeding-season, 

 but at Drigg young are fed chiefly on fish (sand-eels). Insects 

 taken include coleoptera (Aphodius, Geotrupes, Philonthus, Loricera, 

 Agriotes (larvae) and Melolontha), diptera (especially Tipula and 

 larvae), hymenoptera (black ants), lepidoptera (ghost moth and 

 larvae of many species), odonata and neuroptera {Ephemera, etc.). 

 Also mollusca (slugs and snails), annelida (Lumbrici), Crustacea 

 (Amphipoda, Crangon, etc.) ; millipedes, centipedes, occasionally 

 even small birds (Anthus, Phylloscopus), mice (Mus), and eggs of its 

 own and other species. Vegetable matter has also been recorded ; 

 cereals not uncommonly, also seeds of various plants and vegetables 

 (potato, turnip, etc.). 



VOL. II. 3 B 



