THE SOUTHERN GUILLEMOT. 



199 



Central tail-feathers of" 

 A. The Razorbill (A. 

 torda), B. The Guil- 

 lemot ( U. aalge). 



3rd 8-10 shorter, 4th 18-20 shorter, 5th 28-32 shorter. Outer 



secondaries 10-15 mm. shorter than 10th primary, inner ones about 



equal to 9th, tips rounded. Tail slightly rounded, 12 feathers, tips. 



rounded. Bill compressed, culmen 



sloping gently to tip which is obtusely 



pointed, with a notch before tip, 



gonys long, sloping gradually upwards 



to tip in a slightly concave line, 



angle rather prominent ; proximal 



portion of bill feathered except along 



gape where on each mandible is a 



narrow horny ridge. Rest of structure 



as in Razorbill. 



Soft parts. — Bill black, inside 

 mouth yellow ; legs and feet ochreous 

 but posterior portion of tarsus, joints 

 of toes and webs brown-black ; iris 

 brown-black (juv. whitish). 



Characters and allied forms. — For 



differences of U. a. aalge see under 



that form ; U. a. calif ornica (N. 



Pacific) is larger and has a longer, 



thicker bill. For differences of Briinnich's Guillemot see under 



that species. Compressed, tapering bill, "furrow" behind eye, 



black stripe on side of head in winter distinguish it. 



Field-characters. — Usually associated with Razorbill at breeding 

 stations ; like it rides high in the water, flies with rapidly whirring, 

 narrow wings close to surface and, at times, in strings, but is rather 

 larger, of more slender build, has pointed black bill, brown upper- 

 parts and only obscure wing-bar. The note which has been 

 rendered " murre " and " aaar," comes from the packed nesting 

 ledges as a continuous rumbling growl. 



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

 companionship with other species such as Razorbill, Kittiwake, 

 Puffin, etc., and lays on ledges of perpendicular sea-cliffs, or on 

 top of isolated stacks. No nest : egg laid on bare rock. Egg. — One 

 only, pyriform, yellowish when viewed from inside except when 

 overpowered by green of outer colouring. Variation in colour and 

 markings extraordinary ; deep blue-green, bright reddish, warm 

 ochreous, pale bluish, creamy and white types may be met with, 

 marked richly or sparingly with blotches, spots, zones or intricate 

 patterns of interlacing lines which vary in colour from light yellowish 

 brown to bright red, rich brown or black; sometimes quite unmarked. 

 Average size of 90 eggs from Great Britain, 83.03x50.39. Max. : 

 92.7x50.1 and 85.7x52.2. Min. : 72.5x50 and 84.1x43.8 mm. 

 Breeding -season. — Begins about third week May and generally end of 

 month. Incubation. — By both sexes. Period 30, 31, 33 days. 



