94 A HISTORY OF BIRDS 



These are Professor Palmen's main routes, the minor channels 

 of these vast streams being formed by river-courses. 



The great migration routes, as we have already remarked, 

 run north and south, but there are cases where an exceptionally 

 wide easterly or westerly trend is to be noted. These, it is 

 significant to notice, occur mainly where the migrants are com- 

 pelled to follow a shelving coast-line, where a course due north 

 or south, as the case may be, would carry them out into trackless 

 wastes of ocean. Tytler's Swallow, for example, nests in Kams- 

 chatka and winters in Burma. " In New Zealand," wrote 

 Professor Newton, "there are two Cuckoos which are annual 

 visitors ; one, a species of Chrysococcyx, probably has its winter 

 quarters in New Guinea, though commonly supposed to come 

 from Australia, the other, Eudynamys taiiensis, is widely spread 

 throughout Polynesia. . . ." Here are two nearly allied forms 

 which take opposite directions — east and west — yet each follow- 

 ing land routes, and the objective of each, be it noted, being ' 

 north or south as the season may determine. 



More remarkable is the case of the Red-footed Kestrel 

 (Erythropus amurensis) of Eastern Siberia, which winters in 

 Eastern South Africa, more especially, apparently, in the 

 Zambesi region. So far as can be made out at present this 

 enormous journey is not made westward through Arabia and 

 by way of the Nile Valley and the Great Lakes, but across the 

 Indian Ocean. This conclusion has been arrived at, because so 

 far no specimens of this species have yet been taken on the 

 route just referred to, but examples have been taken in the 

 Indian Peninsula, in Cachar and in Canada. This is the more 

 inexplicable because the nearly allied European Red-footed 

 Kestrel {Erythropus vespertinus) — which differs from its Siberian 

 relative only in having the under wing coverts grey instead of 

 white — nests in South- Eastern Europe and winters in South- 

 Western Africa, though the two species are occasionally found 

 together in their winter quarters. Time may show that the 

 Siberian bird after all follows an overland route, but eastwards 

 by the Nile and the Great Lakes, while those birds found in the 

 Indian Peninsula stray no farther southwards. But on the whole 

 it seems clear that though an east to west course, and vice-versd, 

 is followed by some species when on migration, the ultimate 

 goal of all is always north and sputh. ^ 



