FIELD STUDY IN ORNITHOLOGY. 467 



mens liud been .snbseqiieiitly ticketed; Le Vaillaiit described uiaiiy of 

 his South African birds from memory. Thus Latham, after describing 

 very accurately h'hipidiira Jiahellifcra, from the soutli ishmd of New 

 Zeahind, remarks, apparently on Forster's authority, that it is subject 

 to variation; that in the island of Tanna another was met with, with a 

 different tail, etc., and that there was another variety in the collection 

 of Sir Joseph Banks. Endless perplexity has been caused by the Psit- 

 tacii.sj^Hf/Difvus of (Imelin (of which Latham's type is at Vienna) being 

 stated in the inventory as from I>otauy Bay, by Latham from Otaheite, 

 and in his book as inhabiting several of the islands of the South Seas, 

 and now it proves to be the female Psittaeus palmarnm from the New 

 Hebrides. These are but samples of the confusion caused by the inac- 

 curacies of the old voyagers. Had there been in the first crew who 

 landed on the island of Bourbon, I will not say a naturalist, but even a 

 simple-hearted Leguat, to tell the artless tale of what he saw, or had 

 there been among the Portuguese discoverers of Mauritius one who 

 couhl note and describe the habits of its birds with the accuracy with 

 which a Poulton could record the ways and doings of our Lepidoptera, 

 how vastly would ourknowledgeof a perished fauna have been enriched ! 

 It is only since we learned from Darwin and Wallace the power of iso- 

 lation in the differentiation of species, that special attention has been 

 Ijaid to the peculiarities of insular forms. Here the field naturalist 

 comes in as the helpful servant of the philosopher and the systematist, 

 by illustrating the operation of isolation in the differentiation of siDCcies. 

 I may take the typical examples of two groups of oceanic islands, dif- 

 fering as widely as possible in their position on the globe — the Sand- 

 wich Lslauds, in the center of the Pacific, thousands of miles from the 

 nearest continent, and the Canaries, within sightof the African coast — 

 but agreeing in origin, the ocean depths close to the Canaries and 

 between the different islands varying from 1,500 to 2,000 fathoms. In 

 the one we may study the expiring relics of an avifauna completely dif- 

 ferentiated by isolation ; in the other we have the opportunity of trac- 

 ing theincipient stages of the same process. 



The Sandwich Islands have long been known as possessing an avi- 

 fauna not surpassed in interesting j)eculiarity by that of New Zealand 

 or Madagascar; in fact, it seems as though their vast distance from 

 the continent had intensified the inflviences of isolation. There is 

 scarcely a passerine bird in its indigenous fauna which can be referred 

 to any genus known elsewhere. But until the very recent researches 

 of Mr. Scott Wilson and the explorations of the Hon. W. Kothschild's 

 collectors it was not known that almost every island of the group pos- 

 sessed one or more representatives of each of these peculiar genera. 

 Thus every island which has been thoroughly explored, and in which 

 any extent of the primeval forest remains, possesses or has possessed 

 its ow n peculiar species of Hemujmtthus, Hiniatione, Phcvornis, Acriilo- 

 cercm^ Loxops, Brepanis^ as well as of the massive-beaked finches, 



