100 From Magazines, &c. [ ^ J 



Emu 

 Oct. 



and Mammals, American Museum of Natural History, deals 

 succinctly with the migratory movement. In the main he is in 

 accord with the " Principles Governing Movement in Cuckoos 

 and Migration of Birds," as expressed by Mr. A. H. E. Mattingley, 

 C.M.Z.S., in The Emu, v., p. 145, and vi., p. 33, wherein it has 

 been shown that the movement is not attributable to instinct. 

 The extent of the seasonal movement varies in different species, 

 mainly in accordance with the nature of their food, and is also 

 more or less correlated with their powers of flight. There is 

 every degree of migratory movement in different species of 

 birds, from slight nomadic movements to extended migration in 

 :cordance with the physiological needs of the species. The 

 life of a bird, like that of most animals and plants, is made up 

 of annual cycles. The controlling force that governs these 

 cycles and determines the manner of life of the species is 

 the fundamental fiat of Nature — "to increase and multiply" — 

 the perpetuation of the life of the species. The influence 

 governing the selection of a breeding-site is the approach of the 

 breeding season. The cause of the seasonal movement or 

 migration is thus beyond question physiologic, and hence 

 periodic and irresistible. If climatic conditions were everywhere 

 uniform, there would be no migration. Migratory birds, of 

 whatever class, which seek high latitudes for breeding stations 

 find there the conditions most favourable for reproduction as 

 regards not only food but the general environment. The sole 

 and all-sufficient cause of migration is the necessity of a 

 congenial environment for the reproduction of the species. 

 The inception of the movement is the periodic necessity of 

 reproduction, and the journey to the breeding station, be it long 

 or short, is made in obedience to physiologic changes which the 

 bird is powerless to resist or control. The return journey is a 

 natural and necessary sequence. Except figuratively speaking, 

 one cannot ascribe the cause of the migratory movement to 

 " strong home-love." Young birds when left behind join the 

 general throng of migrants, which includes birds of many species. 

 The migratory habit is of the highest antiquity, and is an 

 inseparable part of the evolution of the species. It is a 

 specific trait of their physical characteristics. Many birds 

 not much unlike existing types — belonging in many instances 

 to the same genera — existed in tertiary times. Since this 

 period the earth's surface has undergone great physical and 

 climatic changes, which have in turn immensely modified not 

 only the distribution but the physical characters of its 

 inhabitants. These facts furnish good ground for the belief 

 that bird migration, possibly already incipient at this remote 

 period, became emphasized and mainly developed by the 

 recession of glaciation. It is recognized that birds are endowed 

 with tiie ability to remember and recognize land-marks, hence 



