804 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



uniform white ; axillaries and under wing-coverts white but usually 

 with narrow brown tips ; tail and wing as adult but browner and 

 white wing-coverts with black-brown tips making wing-patch 

 mottled. Tail-feathers, primaries and secondaries grow with rest 

 of juvenile plumage and not with first winter as in Razorbill and 

 Guillemot and feathers are not of such loose structure as in those 

 species. 



First winter. — Much like adult winter but white tips to feathers 

 of mantle narrower and with usually some retained juvenile feathers 

 especially scapulars ; under-parts usually with good many retained 

 juvenile feathers with speckled tips on sides and vent ; wing and 

 tail-feathers and wing-coverts as juvenile. The juvenile body- 

 plumage is moulted (varying number of feathers being retained) 

 Sept. (sometimes Aug.) to Bee, but not wing or tail-feathers nor 

 wing-coverts. First summer. — Body-moult as in adult but rather 

 later and sometimes still moulting in May. Sometimes body -plumage 

 like adult but rather browner and less glossy, sometimes good many 

 white or partially white feathers on under-parts ; tail and wing- 

 feathers brown and abraded and wing-coverts tipped brown as in 

 juvenile. 



Measurements and structure. — $ wing 156-169 mm., tail 44-51, 

 tarsus 29-33, bill from feathers 29-35 (12 British measured). ? wing 

 154-165, bill 29-34. Primaries : 1st longest, 2nd 2-4 mm. snorter, 

 3rd 5-8 shorter, 4th 10-15 shorter, 5th 18-22 shorter. Rest of 

 structure as in Common Guillemot, but occasionally 14 tail-feathers, 

 no " furrow " behind eye, gonys short, bill not feathered so far 

 forward, nostril mostly exposed in a deep groove. 



Soft parts. — Bill black, inside mouth vermilion (orange in 

 juvenile and 1st winter) ; legs and feet bright coral-red (reddish- 

 brown in juvenile and 1st winter) ; iris brown. 



Characters and allied form. — U. g. mandtii (Circumpolar Seas) 

 has finer bill and in juvenile and first winter and summer second- 

 aries have some white at tips. Large white wing-patch distin- 

 guishes Black Guillemot from other British " Auks." 



Field -characters. — Adult in summer is unmistakable. Black 

 plumage is accentuated by a large and conspicuous white wing- 

 patch, vermilion feet and inside of mouth ; latter visible when bird 

 utters its thin whistling cry. Plumage of adults in winter and of 

 young, white below and mottled black and white above, is hardly 

 less distinctive. 



Breeding-habits. — Breeds socially to some extent, several pairs 

 often nesting not far apart, but not so markedly as other Alcm. No 

 nest but eggs deposited on rock in crevice of cliff, in hollow among 

 loose boulders or even in walls. Eggs. — Two normally, while 3 

 have been met with occasionally but rarely ; white, often with a 

 tinge of bluish-green, spotted or blotched with blackish-brown and 

 ash-grey. Average of 80 eggs, 58.6x39.74. Max.: 66.3x38.6 

 and 58x42.2. Min. : 51.2x37.3 and 56.9x32.2 mm. Breeding- 



