SHIP- AND WIND-BOTINE COLONISTS 313 



to make this bird rise from the ground, and, unless it is hard 

 pressed, it never attempts to fly ; yet, after the fashion of its 

 family, it has become a pioneer. 



A widely distributed species of heron, Dcmicgretta sacra, 

 breeds in fair numbers in the islands, and a few wind-blown 

 migrants, swallows, wagtails, snipe and plover, occasionally 

 land, always in very poor condition. The bulk of the avi- 

 fauna of the islands of course consists of the sea-birds pure 

 and simple ; — the frigates, boobies, bo'swain birds and terns : 

 and it is remarkable that the three species of terns, which 

 breed in such numbers on the atoll, are not represented in the 

 Christmas Island fauna. 



Since the atoll lies in the south-east Trade zone, and the 

 wind blows from the S.E., E.S.E., or E. for three hundred 

 days in every year, it might be thought that the place of origin 

 of the greater part of the fauna of the atoll would be a very 

 easy thing to determine. It would be presumed at once that 

 Australia was the fatherland of the bulk of all the living things 

 of the islands — and very many of the forms are Australian. 

 But it is a well-known fact, to which I believe Wallace first 

 called attention, that it is the abnormal rather than the normal 

 winds which are the most important in bringing waifs to dis- 

 tant tracts of land. The dragonflies show the truth of this, 

 for their advent certainly follows the rare northerly and north- 

 easterly winds. 



The terrestrial fauna is therefore not entirely Australian, 

 or even Austro-Malayan, for it contains a very considerable 

 admixture of Indo-Malayan forms, just as does that of its 

 neighbour Christmas Island. 



