ZOOLOGY. 63 



V 



Many of the Aquatic Birds build floating nests ; in the 

 composing of which they interweaTC 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 

 enly 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 his 

 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 

 used to regulate their agricultural operations : — That of the 

 Sioallozo 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 tha 

 jiioaths of summer. 



