THE SPRING MIGRATION OF BIRDS. 209 



birds is gradual, weeks and even months separating 

 the date of appearance of certain species. This 

 seems entirely due to the fact that spring in tem- 

 perate regions lasts for about a couple of months ; 

 but in the Arctic regions, where winter passes into 

 summer with scarcely a day's spring between them, 

 the arrival of migratory birds is sudden and much 

 more simultaneous. Migration in these high 

 latitudes depends almost absolutely upon the break- 

 up of the ice, which may be a few days earlier or 

 later according to local influences. Two of the 

 most complete and graphic records of the spring 

 migration of birds in the Arctic regions are those 

 made by Mr. Seebohm ; the first in the valley of 

 the Petchora (in company with Mr. J. A. Harvie- 

 Brown) during the spring of 1875 ; and the second 

 in the valley of the Yenesay during the spring of 

 1877. Both Migrations are very much alike in their 

 general aspects and conditions. In each case little 

 migration was observed until the ice on the rivers 

 began to show signs of dissolution. Such Nomadic 

 Migrants as Bullfinches, Snow Buntings, and Red- 

 poles were the first to make their appearance, birds 

 that had wintered close to the fringe of perpetual 

 winter snow. Soon after these birds arrived, the 

 Hen Harrier {Circus ajaneus) and the Merlin 

 {Falco cesalon) appeared upon the scene, evidently 

 having followed their prey from the south ; and 

 as soon as these little Finches moved further 

 north or into the forests their enemies followed 

 them. About a week later (May loth in the 



