156 THE BIOLOGY OF BIRDS 



guillemot does not interfere with its neighbour's egg or 

 progeny. 



Razorbills are near relatives of guillemots, but may be 

 distinguished by the laterally compressed bill, with white 

 line: on it, and by the strong white line running from beak 

 to eye. The plumage of the under parts is of the same 

 brilliant white colour, but the dorsal parts are black with a 

 greenish gloss, while the throat and foreneck show velvety- 

 brown. From our biological standpoint it is interesting to 

 contrast two nearly-related species, which might be called 

 " second cousins," to see how individuality finds detailed 

 expression along many lines. Both birds incubate a single 

 egg for thirty daj^s, but the variability in the external colour- 

 ing of the razorbill's egg is distinctly less than in the case of 

 the guillemot's. Moreover, the interior of a razorbill's 

 eggshell held against the light is greenish, whereas it is 

 yellowish-white in the case of all guillemots, except when the 

 outside of the shell is blue-green. Both birds are mono- 

 gamous, but they differ in their courtship ceremonial. In 

 both types the young bird is fed on small fishes, but the 

 guillemot carries one at a time lengthwise, while the razorbill 

 carries several crosswise. Such is specificity. 



Another bird of the cliffs is the puffin, belonging to the 

 same auk family (Alcidae) as the guillemots and the razorbills. 

 It is a highly individualised bird, marked by the stocky form, 

 short neck, orange-yellow legs, and large, laterally compressed 

 bill, brilliant in scarlet, blue, orange, and white. When 

 alert it stands bolt upright and look as if it were resting on 

 its tail. But this is, of course, an illusion. It is only when it 

 walks about or crouches for a spring that the puffin plants 

 more than its toes on the ground. When it is resting at its 

 ease its pose sinks from the upright to the horizontal. 



Just as razorbills and guillemots are usually found on 

 different sections of the cliff-face, so the puffins often keep 

 to themselves, preferring the top of the cliff where there is 

 some soil in which they can burrow ; for a rough grass 

 nest is made at the end of a tunnel which may be a yard 

 long. As already noted, this is usually excavated, hut a 



