040 MIGRATION 



Swifts delight in sultry thundry weather, and seem thence to 

 receive fresh spirits. They fly in those times in small parties with 

 particular violence ; and as they pass near steeples, towers, or 

 any edifice where their mates perform the office of incubation, 

 emit a loud scream, a sort of serenade, as Mr. White supposes, 

 to their respective females. 



[Pennant. 



SECTION XVIII. 



On the Migration of Birds. 



It is believed that many different kind of birds annually pass 

 from one country to another, and spend the summer or the winter 

 where it is most agreeable to them ; and that even the birds of our 

 own island will seek the most distant southern regions of Africa, 

 when directed by a peculiar instinct to leave their own country. 

 It has long been an opinion pretty generally received, that swal- 

 lows reside during the winter-season, in the warm southern regi- 

 ons ; and Mr. Adanson particularly relates his having seen them at 

 Senegal, when they were obliged to leave this country. But be- 

 sides the swallow, Mr. Pennant enumerates many other birds which 

 migrate from Britain at different times of the year, and are then to 

 be found in other countries ; after which they again leave these 

 countries, and return to Britain. The reason of these migrations 

 he supposes to be a defect of food at certain seasons of the year, or 

 a want of a secure asylum from the persecution of man during the 

 time of courtship, incubation, and nutrition. The following is his 

 list of the migrating species. 



1. Crows. Of this genus, the hooded crow migrates regularly 

 with the woodcock. It inhabits North Britain the whole year ; a 

 few are said annually to breed on Dartmoor, in Devonshire. It 

 breeds also in Sweden and Austria : in some of the Swedish pro- 

 vinces it only shifts its quarters, in others it resides throughout the 

 year. Every ornithologist is at a loss for the summer retreat of those 

 which visit us in such numbers in winter, and quit our country in 

 the spring; and for the reason why a bird, whose food is such that 

 it may be found at all seasons in this country should leave us. 



2. Cuckoo. Disappears early in autumn; the retreat of this 

 and the following bird is quite unknown to us. 



