STORM-PETREL 



207 



of the bony palate of the skull, which is of the open type. They 

 differ, however, in that the apertures of the nostrils in the skull are 

 of the oval instead of the slit -like type ; while they are broadly 

 distinguished from all other birds by the circumstance that the 

 nostrils terminate externally in tubes, which may be either separate 

 or united. The latter feature is, of course, alone sufficient to enable 

 any one to recognise a petrel at a glance ; but it may be well to refer 

 to a few other characteristics of the group. In common with some of 

 the members of the cormorant group, all the petrels have the horny 

 sheath of the beak divided by deep furrows into several distinct pieces, 

 and the tip of the beak is sharply bent downwards. The above- 

 mentioned separate pieces of 

 the horny sheath of the beak 

 have been severally identified 

 with the shield-like scales on 

 the heads of lizards ; and if this 

 identification be well founded, 

 it would seem that a beak of 

 the petrel-type is the original 

 form from which has been 

 derived that of ordinary birds, 

 covered by an undivided horn- 

 sheath. This, however, is by the 

 way ; and to revert to the char- 

 acteristics of the present group, 



it may be noted that the three front-toes are webbed, and that the hind 

 one is never large and may be altogether wanting. In the generally 

 long wings there are eleven primary quills ; the oil-gland is tufted ; 

 and the feather-bearing tract in the spinal region is well defined on 

 the sides of the neck by featherless areas, and forms a fork on the 

 lower part of the back. 



All petrels, except during the breeding-season, are essentially birds 

 of the open sea, and display a remarkable range of variation in bodily 

 size ; the species to be immediately considered being scarcely lar^-er 

 than a sw^allow, w^hile the lordly albatross exceeds in wing-span every 

 other living bird except the condor. In the case of most species only a 

 single egg is laid by the female ; this being generally deposited in a 

 burrow dug by the bird itself As a rule, the eggs are white, but they 

 may have a zone of reddish dots at the larger end. Both sexes are 

 alike in plumage, there is only a single moult, and the young are help- 

 less and clad in down till full-grown. Small fishes, crustaceans, and 



THE ROWLAND 



STORM-PETKEL (MALE). 



