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Further, it has yet to be determined to what extent 

 light of itself attracts the flocks which happen to be on 

 its level, or whether it ever draws them down from 

 the upper regions. 



It will have doubtless been remarked that the state- 

 ments hitherto made, and the conclusions drawn therefrom, 

 have had almost exclusive reference to the Northern 

 Hemisphere ; but such must needs be the case in the 

 present state of our knowledge, for we cannot as yet 

 judge accurately of what takes place to the south of the 

 Equator, owing to the absence of precise information as 

 to the movements of birds there, and the comparatively 

 small number of qualified observers in those regions 

 interested in the subject. 



Yet even thus it is allowable to express an opinion — 

 though as yet only an opinion — that, mutatis mutandi.^, 

 the state of affairs in the Southern Hemisphere will not 

 prove very dissimilar to that in the Northern, since the 

 evidence, such as it is, afforded by New Zealand is to 

 the foregoing effect. 



Migration of the nature described in the foregoing 

 paragraphs may be called Normal Migration, while the 

 members composing the flocks are the True Migrants. 

 At the same time it must be observed that all birds 

 do not cover equal distances on their journeys. It is 

 probable, with regard to many species, that the individuals 

 which are most capable of flight, or perhaps those that 

 start upon their travels earliest, go further than the 

 remainder are able to do, and so outstrip their fellows 

 both in autumn and spring ; but, leaving such out of 

 consideration for the moment, it is evident that the 

 general movements will result in a shifting of the bird 

 population to approximately equal distances in the case 

 of the true migrants, all of which leave their summer 

 homes when reproduction is over, and, after exhibiting 

 themselves in the character of birds of passage in the 



