INTRODUCTION. 



Petrels apparently belong to an ancient race of birds, as their remains have been 

 found in a fossil state in various parts of the world, though mostly in superficial 

 deposits ; Diomedea anglica, however, is known from the Red Crag of Norfolk 

 (Lydekker, Cat. Fossil Birds in Brit. Mus.). 



The Order Tubinares embraces Families differing in external appearance to an 

 extraordinary degree, and varying in size from the tiny Storm Petrel to that of the 

 Wandering Albatros. The greater number of the species are of powerful flight, 

 fitted to combat oceanic storms, in which the larger ones in particular appear to delight. 



The members of the Family Pelecanoididse, however, which are peculiar to 

 the southern oceans, and resemble the Little Auk of the northern seas both in 

 appearance and habit, frequent sheltered bays in preference to open waters, and procure 

 their food by diving, for which they are specially adapted. Notwithstanding these 

 wide differences, Petrels may at once be distinguished from all other birds by their 

 prominent tubular nostrils, and by their bills, which consist of several horny pieces 

 separated by deep grooves. 



Petrels are dispersed throughout all the oceans of the world, penetrating to the 

 Ice Barrier at both poles, though they are probably more numerous in the southern 

 than in the northern hemisphere. They are purely oceanic wanderers, and unless 

 driven ashore by storms, seldom, if ever, come to land except for the purpose of 

 breeding, and then they invariably select unfrequented rocks and islands difficult 

 of access. All the smaller species nest in burrows in the ground, or in the clefts of 

 rocks, and are more or less crepuscular in habit. 



Considering the vast number of these birds inhabiting the seas, it seems 

 remarkable at first sight that so much difficulty is experienced by our Museums in 

 obtaining examples, but this, of course, is due to their mode of life, and the great 

 difficulty in securing specimens at sea. It must also be remembered that many 

 species resemble each other very closely and the slight differences between them 

 are not easily identified from the deck of a passing ship, even by a competent 

 observer, hence much that has been written on the occurrence of certain birds in 

 stated localities must be received with caution. 



With regard to the plumage, much more information is still required as to the 

 various stages through which the birds pass before reaching the adult. Some 

 doubtless assume the mature plumage as soon as they are fully grown, while 

 others, such as certain of the Albatroses, take years before they acquire their full 

 dress. Again, much remains to be learned respecting the colour of the legs and bill, 



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