OQ Introduction: Variation. 



of Celebes and the Philipi)ines, and not Celebes and the Philippines from them; 

 their volcanic or coral character see de Hollander, Land- en Volkenkunde 

 Ned. Oost. Ind. 18S4, XL 234; and the absence of heavy, ill-flying birds and of 

 peculiar generic types speak for the recent upheaval and colonisation of these 

 islands'). It might happen that a species or two on the mainlands subsequently 

 became smaller, but there is no reason to assume that the twenty species which 

 remained in Celebes and the Phili])pines all became small hereafter, while those 

 which had peopled the islands all maintained the original sizes of the species. 

 On the other hand there is reason to anticipate that the individuals of these 

 twenty species which had emigrated to the new islands would undergo alteration 

 of some kind or other, for the conditions of existence are not precisely the 

 same there. It appears, therefore, quite safe to assume that Celebesian and 

 Philippine birds develop as a rule into larger races in Sangi and 



Talaut'^). 



As is usual in such cases it is not difficult to find more than one explan- 

 ation why these things should be so, but not easy to decide which explanation 

 is the true one. The most plausible suggestion is that the dangers are fewer 

 and the struggle for partners perhaps more severe in Sangi and Talaut than on 

 the mainland. Hawks and Falcons which prey upon birds seem to be very 

 rare in these islands; so far not one bii'd-eater, strictly speaking, has been killed 

 in them, for Tachj/spizias soloensis, the most dangerous to small birds, is not 

 only a migrant but feeds to a great extent on insects. Moreover there are no 

 monkeys in Sangi and Talaut, and other enemies, which could be dangerous to 

 breeding birds, their nestlings and eggs, are rarer than in Celebes and the Phi- 

 lippines. The chief competition therefore that goes on would appear to be 

 among the birds themselves, and the largest and strongest will be more likely 

 to secure nesting quarters and partners than the smaller and weaker'). 



Decrease in size in Sida. — Two Birds -of- prey and two Pigeons display [a 

 slight reduction in dimensions in the Sula Islands, viz. Spilornis rufipectus, Acci- 

 piter sulaensis, Ttiracoena manadensiji and Macropygia albicapilla. Sula seems to 

 resemble Celebes in its Birds-of-prey. 



Differences in size in the North and Soitth Peninsulas of Celebes. — As a rule 

 the birds agree in their dimensions in these districts, but where there is a differ- 

 ence it seems to be in the direction of an increase in size in South Celebes. 

 Pachycephala meridionalis and Stoparola vieridionalis are much larger than the 



I 



•) Prof. Hickson noticed evidences of recent slight elevation in Talaut (Nat. in N. Celebes 1859, 151, 157 . 



-] The case affords a good illustration of our postulate, that colonists become more changed than staj'ers- 

 at-home 'see, p. 162;. 



•') It may be added that many ornithologists are of opinion that the males of most species of Ijirds are 

 more numerous than the females, and Dr. Platen certainly collected many more males than females in the 

 Sangi Islands (see W. lilasius, Omis 1888, pp. 527— G46 ; but it may well be that the superior plumage of 

 the males leads to their being shot and skinned more frequently, and it is preferable not to introduce this 

 doubtful element into the argument. 



