BLACK GUILLEMOT. 313 



usually flying off at once to the water, there to remain 

 until the danger has passed. 



Range of egg colouration and measurement : 

 The eggs of the Black Guillemot are two in number, 

 smaller and blunter than those of the Common Guillemot, 

 and resembling those of the Razorbill in general colour- 

 ation. They vary from cream to buff and pale green in 

 ground colour, blotched, spotted, and more rarely streaked 

 with rich dark brown and paler brown, and with numerous 

 and large underlying markings of gray. Usually the 

 blotches and spots are pretty evenly distributed over the 

 entire surface, but zones are not uncommon. Average 

 measurement, 2"35 inches in length, by v6 inch in 

 breadth. Incubation, performed by both sexes, is said 

 to last twenty-four days. 



Diagnostic characters : The eggs of the Black 

 Guillemot may be readily distinguished from those of 

 allied species by their much smaller size. They resemble, 

 however, certain varieties of those of the Sandwich Tern, 

 but may be at once distinguished by their greater weight 

 and greenish tinge. Ihe site on which they are laid 

 also prevents the slightest possible chance of confusion. 



Family ALCID.E. Genus Alca. 



RAZORBILL. 



Alca torda, LiitncEus. 



Single Brooded. Laying season, middle of May to middle of 



June. 



British breeding area : The Razorbill is widely 

 and commonly distributed along all rocky coasts suited 

 to its requirements, although nowhere perhaps so 



