CONCEALED OR COVERED NESTS 99 



are viewed — assisting to make the comparison 

 complete. 



The last group of typical burrowing birds that I 

 shall notice here is the Petrels, forming the great 

 natural order Procellariiformes. We have already 

 had occasion to glance at the domestic arrangements 

 of some of these birds building crude nests in the 

 open. The majority of species, perhaps, breed in 

 places where the eggs are concealed from view, and 

 not a few of the birds tunnel into the ground to 

 secure that purpose. Beginning with the more 

 familiar species we may instance the nest burrow 

 of the Stormy Petrel (Procellaria pelagica). This 

 tiny bird — the smallest known web-footed species — 

 always endeavours to secure a burrow ready made, 

 the discarded hole of some other creature, or failing 

 that will seek a nesting-place under rocks or in heaps 

 of stones or masonry; but in some localities it is 

 compelled by circumstances to excavate a tunnel for 

 itself. This is rarely more than a foot or two in 

 depth, at the end of which it forms a bed of dry 

 grass for its solitary egg. Another, and much rarer 

 species, the Fork-tailed Petrel (P. leachi), breeds locally 

 on the western coasts of our islands. This species 

 is a much more elaborate excavator, its burrows 

 sometimes extending as many as six feet, but more 

 usually four or five feet. This burrow is seldom 

 straight, but winds about in a very erratic manner, 

 and often has several outlets. It is usually made in 



