SUPPLEMENT ON THE FISSIROSTRES. 



The habitat of the swallow is said to extend itself to all 

 those parts of the earth's surface in which insects, its prin- 

 cipal food, are to be found. In climates which are exposed 

 to considerable changes of temperature, these birds indeed 

 are only seen periodically ; but in intertropical countries, 

 especially those which border on the temperate zones, as 

 Egypt, Ethiopia, Lybia, &c. they remain during the whole 

 year. The object attained by this phenomenon is principally 

 a continued supply of food, and has probably but little 

 reference to any given degree of atmospheric temperature 

 necessary to these birds, whose country seems almost to be the 

 world at large. 



The cleft beak has furnished systematists with a character 

 whence to name this family of birds Fissirostres, but the 

 rapidity and dexterity of their flight would have afforded a 

 still more striking distinction. They may, with peculiar 

 propriety, be called tenants of the air, since they hunt their 

 prey, and eat it, drink, and occasionally even feed their 

 young, on the wing ; indeed when not under the migratory 

 influence, they may be said to live entirely on the wing and 

 in the nest. Their rapidity is well kno%vn, and the " murder 

 aiming eye" of the most experienced sportsman will seldom 

 avail against the swallow, unless it be at the instant the bird 

 makes an angle in flight, which it is remarkable for doing, 

 probably in the pursuit of some insect out of its direct 

 course ; hence they themselves seldom fall a prey to the 

 raptorial birds, while they commit the greatest havoc among 



