SEA-CLIFFS IN NESTING TIME 139 



of all three species are very handsomely marked, while 

 those of the guillemot are the most variable and some of 

 the most beautiful laid by any British bird. Almost end- 

 less as is the variety of their colour and markings, they 

 are easily recognisable by their peculiarly long and pointed 

 shape. The relative smallness of the little end makes them 

 revolve in a circle when disturbed, instead of rolling forward 

 as a rounder egg does ; and this is often quoted as a specially 

 developed provision, by which the eggs are prevented from 

 rolling over the precipices when the birds take wing on 



guillemot's egg 



a sudden alarm. Some eggs are no doubt saved in this 

 way ; but it is very doubtful whether they owe their shape 

 to this selective process. Many of them are laid in safe 

 crevices ; and the same pointed shape and consequent 

 circular movement are found in the eggs of the snipe, 

 peewits, and the whole tribe of waders, which lay their eggs 

 safely on the flat soil. 



Puffins have adopted a different plan, burrowing like 

 rabbits in the layer of soil that caps the cliffs and islets. 

 After they have departed in late summer, it is singular to see 

 their clustered burrows riddling the sandy shoulder of a 

 cragstack as thickly as a colony of sand-martins' nests, but 

 without a sien of life. At the end of these burrows each 



