MIGRATION. 39 



That these periodical movements take place, in order to 

 guard against the vicissitudes of the seasons, must appeai- 

 obvious to all, from the consideration of the facts which 

 have been stated. An early winter brings the migrating 

 birds from the north to this country before their usual time, 

 and an early spring hastens the arrival of our summer 

 visitants. In the beginning of winter the snow-bunting is 

 found only in the high grounds, and it descends to a lower 

 level with the increasing severity of the season *. 



During the autumn, we thus observe a latitudinal move- 

 ment of many species of birds towards the equator, in 

 search of the temperature congenial to their constitutions, 

 and which the winter of the district of their summer resi- 

 dence could not afford. The autumnal shifting of the fea- 

 thered tribes, may therefore, with propriety, be termed the 

 Equatorial Migration ; all those species in which it is ob- 

 served, returning from the pole towaixls the equator, each 

 according to limits peculiar to itself 



The vernal shifting takes place with the increasing tem- 

 perature of the high latitudes, and may be termed the Polar 

 Migration, as all the species in which it is observed recede 

 from the equator and approach towards the pole. 



" Attempts have been made to preserve these birds during the summer sea- 

 son in this country, but, although liberally supplied with food, they hare 

 not siu-vived. Tlie experiment has succeeded, ho'vever, in America, with 

 General Davies, who informs us, (Linn. Trans, vol. iv. p. 157.) that the 

 snow-bird of that country always expires in a few days, (after being caught, 

 although it feeds perfectly well), if exposed to the heat of a room with a fire 

 or stove ; but being nourished with snow, and kept in a cold room or pass- 

 age, will live to the middle of summer : a temperature much lower than our 

 summer heat proving destructive to these birds. The swallow, on the other 

 hand, seems to delight in the temperature of our summer, and at that heat 

 to be able to perform the higlier operations of nature. When attempted to 

 be kept during our winter, besides a regular supply of food, care must be 

 taken to prevent it from being benumbed with cold. 



