THE SUCCESS OF THE TERNS 221 



in the nesting-season are undoubtedly in the 

 north. 



When we come to consider groups, however, the 

 palm for success in the struggle for existence, as 

 evidenced by wide distribution over the world, must 

 be awarded to the Terns, a very highly specialized 

 group in structure, exaggerating the points of their 

 more generalized family relations the Gulls. Gulls 

 go nearly everywhere, but are much rarer in or 

 near the Tropics than in colder regions, and rarely 

 breed there, and are absent altogether in the 

 Central Pacific. But you cannot go anywhere 

 without meeting Terns, not only in remote islands, 

 but in the interior of great continents, for there 

 are many freshwater species. 



Those curious exaggerations of the Tern type, 

 the Scissor-bills (Rhynchops), with the " under- 

 shot " beak with which they plough the water for 

 small fish, are all warm-climate birds, but the few 

 species between them extend all round the world. 



Although there are no islands too distant for 

 such birds as these and of course the oceanic 

 Petrels to have reached, there are some which 

 are too out-of-the-way for any land-bird. When 

 Mr. W. L. Sclater was sent to investigate the 

 birds of the Chagos Islands, a small group in the 

 Indian Ocean, he found no land-bird there except 

 the little Scarlet Weaver (Foudia madagascariensis), 

 a most obvious human introduction ; and on Easter 

 Island, although a small land-bird has been re- 

 ported, it has never been brought to book, and 



