^Q Introduction: Migration. 



Brewer and Ridg way's "Water Birds of North America" 18S4 I, 123, whether 

 those birds which spend the summer in the winter haunts of their species are 

 not old, effete and barren individuals. This suggestion is negatived by the 

 fact that among such visitors to Celebes five species have been known 

 to breed in some part, or parts, of their winter range, viz. Ckaradrius fulviis, 

 AegiaUtis geoffroyi, A. mongola, Strepsilas interpres and Limosa novaezealandiae. 



Causes of migration. — It may be tritely said that birds, migrate in autumn 

 to feed, in spring to breed! At the approach of winter most birds must of 

 necessity proceed towards the tropics, or starve, owing to the disappearance of 

 their food through death or hibernation, or through concealment under snow or 

 ice. In spring the temperate and arctic regions produce an abundance of food 

 and, it may be presumed, offer safer and easier conditions for the propagation 

 of the species than is found in the tropics; the birds then repair to their native 

 haunts. Naturalists, who seek for j)hysiological conditions to account for the 

 actions of the subject, may find a stimulus for the sjiring migration in the annual 

 develo])mcnt of the reproductive systems, while the approaching autumnal moult 

 of the remiges may sometimes serve as a warning to sjiecies that it is time to 

 accomplish their flight towards the equator, for many of them leave long before 

 the cold sets in. AVaders killed in their winter quarters in the Celebesian area 

 in the late autumn or winter months are generally found to be moulting some 

 of their remiges. Possibly, however, the chief motive for the spring migi-ation 

 is to be found in the love of home so strongly developed in birds, for without 

 this it is conceivable that they would attempt to establish themselves in the 

 tropics for breeding purposes. Instances of the marvellous regularity with which 

 individuals return to the old breeding haunt after a journey of hundreds, or 

 more often thousands, of miles have excited the admiration of all field-observers. 

 That the young birds also sometimes follow their parents to their birth-j)lace is 

 shown by a case given on p. 48 (text). But it seems to be the case — which is 

 not so generally known — that birds display a very similar adhesiveness in the 

 choice of their winter quarters. An instance of enormous numbers of Wagtails and 

 Swallows returning two years in succession to roost in a coffee garden in ('eylon, 

 as observed by Mr. S. Bligh, will be found on p. 537; and Davison states 

 that a large number of migratory Collocaliae, which had taken to roosting upon 

 a certain spot about a yard square against the roof of a shed in the Andamans, 

 disa])peared when the building was pulled down, only to come again and occupy 

 the same spot on a new shed, which had been put up on the identical site 

 (p. 332). There are no rookeries near Dresden, but every year about the be- 

 ginning of November great numbers of Rooks and Jackdaws pass over the 

 neighbourhood for many days in succession'), and some spend the winter there. 



') The flocks fly high, so that it is sometimes difficult to detect them with the naked eye. Tlie mode 

 of progress is very slow in a S. or S.AV. direction, perhaps at the rate of 12 miles an hour, and conducted 

 with much cawing and calling and circling in the air, as if none wish to have the responsibility of leading the way. 



