148 BIRDS' NESTS 



of another somewhat extensive and heterogeneous 

 group of birds, the Pelecaniformes, in which are 

 included the Gannets, Cormorants, Pelicans, Tropic 

 Birds, Darters and Frigate Birds. Some of these 

 species (the Tropic Birds), as we have already seen, 

 are absolutely nestless, yet many of the others con- 

 struct more or less elaborate open nests — which still 

 further emphasises the fact that affinity is not 

 necessarily any indication of uniformity in the type 

 of nest, the latter being influenced, we might almost 

 say, entirely by the conditions of life of each indi- 

 vidual species. Although many of the nests in this 

 order of birds cannot be described as elegant — in 

 fact, most of them are more or less offensive, owing 

 to the ways of life of their builders — they are, on the 

 whole, fairly well made. Yet even these remarks 

 cannot be taken in too literal a sense, for we shall 

 find considerable difference in the degree of finish even 

 in the nests of species belonging to the same genus, 

 and occupying almost precisely the same localities. 

 This is one of the most interesting facts that confront 

 the caliologist during the course of his investigations. 

 First, then, we have to consider the nests of the 

 Gannets (Sulidae). These birds are gregarious, and 

 resort in vast numbers each recurring season to some 

 rock-bound isle to rear their young. Seven species 

 are known ; the majority of these are found in the 

 tropics, two inhabit the Southern Hemisphere, whilst 

 another is confined to the North Atlantic basin. 



