50 THE RIDDLE OF MIGRATION 



As good an example of confusing movements as 

 is to be found in the northern hemisphere, is pro- 

 vided by the white-winged cross-bill (Loxia leucop- 

 tera) of Canada and the States. These birds travel 

 mostly in bands and rove over enormous tracts of 

 territory. They feed on cones and change their 

 grounds whenever the spirit moves them. If they 

 strike a district in which the cone supply is ample 

 they apparently stay there as long as it lasts and 

 then again move on. They have no fixed breeding 

 areas and breed at the appropriate season wherever 

 the cone supply may have landed them. Thus it 

 happens that once in so many years the Edmonton 

 district receives an invasion of these birds. This 

 was the case in the winter of 1920-21 when a par- 

 ticularly heavy influx occurred, reaching far south 

 into the Province. The interesting point is that 

 the birds stayed to breed the following spring and, 

 in fact, did not finally depart till the end of the 

 next winter. These birds must actually have come 

 south from the north in the first place and thus in 

 this instance would actually have reversed our 

 entire conception of northern migrations, should we 

 admit such movements into our scheme. 



This case appears to be analogous with the wan- 

 derings of most species of birds in the subtropics and 

 Australia, whose most characteristic movements, 



