ON THE SYSTEMATIC POSITION OF THE 



PETRELS. 



BY 



W. P. PYCRAFT, F.Z.S., A.L.S., Etc. 



Not the least interesting feature of the Petrels is the fact that, superficially, 

 they bear an undoubtedly close likeness to the Gulls. By the earlier Ornithologists, 

 and even by some at the present day, this likeness has been taken to indicate 

 the close relationship of the two Orders. As a matter of fact, this resemblance 

 is due entirely to convergence, or "homoplasy." That is to say, it is due to the 

 action of a similar environment on fundamentally similar structures. The 

 Owls and the Accipitres afford a similar case. 



But while the Gulls have acquired the ability to roam inland, finding an 

 ample subsistence, the Petrels are, without exception, marine, coming ashore 

 mainly for breeding purposes. 



The Gulls, in the number and coloration of their eggs, and in the condition 

 of their young at birth, resemble the Charadriiformes, of which, indeed, they 

 are unquestionably highly specialized members. The Petrels, on the other hand, 

 lay but a single egg, which is white, in some species relieved by a few frecklings 

 of red spots arranged zone-fashion at one end. This egg, save in the Albatroses, 

 which are nest-builders, is deposited in a burrow, or under ledges of rock and similar 

 crevices. The young when hatched are blind, and remain long helpless in the nest ; 

 while their downy colouring differs materially from that which is observed in 

 Charadriiformes, as will be shown presently. 



In the following pages divergence between the Gulls and Petrels will be set 

 forth, at any rate in broad outline. The facts selected for mention here are such 

 as have a more or less important bearing on questions of taxonomy ; purely 

 morphological details are for the most part omitted, as being foreign to the aims 

 of the present work. But those who desire further information on points raised 



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