90 The Scottish Naturalist. 



than other animals; and it is observed, that in birds enabled to 

 take the highest and longest flights, such as the Condor of 

 South America, Vulture, Eagle, &c., this extention or diffusion 

 of air is carried further than in others, being regulated according 

 to the requirements of the species. 



This is especially exemplified in the formation of the 

 Man-of-War or Frigate-bird {Tachypetes aquilus) of the tropics, 

 whose prodigious spread of wing, in comparison to the size 

 and lightness of the body, together with the slender forked tail, 

 gives it not only a superiority in speed, but from the large pro- 

 portion of caloric with which it must be supplied, a power of 

 susi_)ension enabling it to attain a height perhaps unequalled 

 by any other bird ; however rapidly the various gulls and terns, 

 or even the Tropic or Boatswain bird [Phaeton cethereus) move 

 on the wing, it is to it a mere matter of sport to overtake and 

 rob them of their prey, with a flight so swift, that it has been 

 said that he might with ease secure his breakfast in Africa and 

 his dinner in America. . It has been computed, says Mr Gould, 

 that our swallow has a speed equal to about 90 miles an hour, 

 and that should this be a just computation, that of the Alpine 

 Swift must be twice as great, but that is nothing compared 

 to the Frigate-bird. A French author,* but I know not with 

 what authority, states that the former bird has been computed 

 to accomplish 80 leagues an hour, equal to 240 miles. Even 

 with the lesser speed of the swallow, which can cover a space of a 

 thousand miles in the course of ten or twelve hours, migration 

 seems trivial, in comparison to those who seemingly have neither 

 strength nor expanse of wing to perform the same, such as the 

 willow-wren, and hosts of others, who yet fearlessly hasten on- 

 wards. "We may well be astonished, if we only consider the resolu- 

 tion, the power, that must impel them to undertake this tremen- 

 dous journey, to be accomplished twice every year, traversing seas, 

 crossing mountains, through every diversity of climate, encoun- 

 tering dangers of every kind, till after reaching the northern shores 

 of Africa, and resting awhile, proceed, some to remain in the 

 vicinity, some to occupy the cooler regions of the Atlas, some 

 to winter in the warmer climate of Southern Morocco, and 

 others venturing even to cross the great Sahara itself, and after 

 resting perhaps for awhile on some friendly oasis, finally 

 reaching the more fertile plains of the black man. A few 



*Michelet. '' VOiseau:' 



