Migrations of North American Birds. 291 



sons of the year with the varying declination of the sun. South 

 of this belt, in Georgia, Louisiana, &c., the country is influenced, 

 at certain seasons of the year, by the north-east trade winds, 

 and north of the same belt by the polar winds, which, on account 

 of the rotation of the earth, tend to take a direction toward the 

 west. It must be recollected that the westerly direction of the 

 belt here spoken of is principally the resultant of the south- 

 westerly and north-westerly winds alternately predominating 

 during the year." 



From these considerations and facts, therefore, we are entitled 

 to conclude ihat the transfer of American birds to Europe, is 

 principally, if not entirely, by the agency of the winds, in 

 seizing them during the period of their migration (the autumnal 

 especially), when they follow the coast, or cross its curves, often 

 at a considerable distance from land, or a great height above it. 

 Carried off, away out to sea, mainly from about the latitude of 

 45'^ (the line of greatest intensity of the winds) the first land 

 they can make is that of England, whence the fact that most of 

 the species have occurred in the British Islands as well as 

 Heligoland, equally well fitted to attract stragglers and furnish 

 them a resting-place. It is probable that, apart from their few 

 permanent residents, the Bermudas are supplied in the same 

 manner. 



Iceland being in the latitude of the reverse current, from east 

 to west, such of its species as are caught up by the winds and 

 carried off would soon reach Greenland, only a few hundred 

 miles distant. This may be the principal agency of supply from 

 Europe to Greenland, as most European land-birds are only met 

 with there at rare intervals, although, as Greenland lies north of 

 Iceland, there may be a regular migration to some extent. 



As remarked, the prevailing direction of the winds, whether 

 violent or moderate, throughout the year, as well as during the 

 period in which our birds are on either their spring or autumnal 

 migration, is from America toward Europe. Even should their 

 direction be reversed and that rare phenomenon, a summer 

 " north-easter," occur, it would merely have the effect of bring- 

 ing the birds back upon our coast, or into the interior, the 

 line of the storm being in fact about parallel with the eastern 



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