ZOOLOGY. 



65 



Many of the Aquatic Birds build floating nests ; in the 

 composing of which they interweaye the stem or leaf of some 

 living aquatic plant, by which their nests are secured from 

 being carried away by the stream ; and some kinds even use 

 ©nly so much of the living plant as may keep them secure, but 

 at the same time permit the nest to rise or fall with the water ; 

 other kinds on quitting the nest (for food,) cover the eggs 

 with decaying vegetables^ to screen them from observation. 



Birds are generally monogamous, only living together in 

 pairs during the spring Months, or whilst rearing their 

 young ; after which they keep separate till the ensuing spring. 

 Some few species keep constantly in pairs ; as the Raven 

 and some of the larger Birds of prey ; whilst others, as the 

 Gallinaceous kinds, are polygamous, each male having hi§ 

 seraglio of females. 



The migration of Birds forms a remarkable feature ia 

 their history, and is deserving the greatest attention; by 

 the arrival or departure of different species, our forefathers 

 Vised to regulate their agricultural operations : — That of the 

 Swallow has ever been a theme of admiration ; their sudden 

 appearance and departure has induced such a variety of opi- 

 nions, that Naturalists are quite divided upon this point ; 

 this diversity of opinion has been occasioned by the sudden 

 appearance of a straggling bird, during warm days, early in 

 the spring. On the seventh of February, in the present year 

 (1817), we observed a single chimney Swallow, flying about 

 with all the alacrity so conspicuous in this tribe during the 

 months of summer. 



