392 PETRELS AND SHEARWATERS 



grey, or brown in colour, but always " self-coloured." In these two 

 last particulars the Petrels resemble the Penguins. 



The Gulls have, as it were, demonstrated their plover-like affinities 

 in sending more or fewer species inland to follow the plough, and 

 play the scavenger up and down rivers and other inland waters often 

 remote from the sea. With the Petrels this is never the case. All 

 are strictly marine species, never leaving the extreme edge of the 

 coast, never straying out of sight or sound of the sea. And thus it has 

 come about that some species have become so highly specialised that, 

 like their remote relatives the Grebes and Divers, they have acquired 

 the art of obtaining their food from the depths of the sea instead of 

 its surface ; as witness the little diving-petrel, Pelecanoides. This 

 bird, however, affords a parallel in another direction. It has come 

 to bear so close a likeness to the little-auk that the inexpert might 

 readily mistake the one for the other, and the little-auk, of course, 

 is a specialised member of the Limicolse. 



Such, then, are some of the features that the Petrels present for 

 those who are fond of speculating on the relation between the 

 bodily form and habits. Other features of no less interest will 

 become apparent as we proceed. 



STORM-PETRELS 



The "Storm-Petrels," which form the Family Procellariida?, are 

 distinguished from the remaining members of the order by a number 

 of well-marked characters, the most conspicuous of which are the 

 great length and slenderness of the legs, and the character of the 

 aperture of the external nares, which open into a common chamber. 

 All are conspicuously long-winged and relatively small species, and 

 dusky in coloration, though some have a large white rump-patch. 



On the British list five species are recorded, but of these only 



