282 MIGRATION OF ANIMALS. 



known to assemble in immense numbers before the period of 

 their migration. Some birds, however, have never been ob 

 served to gather together previous to their departure. Tht 

 males of many species appear to perform their migrations a 

 few days before the females. This is remarkably the case 

 with the nightingale. Others depart during the night. In 

 short, the habits of birds, with regard to their migrations, differ 

 according to their characters and habits in other respects. 



' It has been objected to the migration of birds, that it is 

 impossible they should support themselves so long upon the 

 wing, or exist so long without food, as they must probably do 

 in performing such long journeys as migration supposes. 

 " But these difficulties," says Dr. Fleming, " vanish altogether 

 when we attend to the rapidity of the flight of birds. The 

 rapidity with which a hawk and many other birds occasionally 

 fly, is probably not less than at the rate of 150 miles an hour. 

 Major Cartwright, on the coast of Labrador, found, by repeated 

 observations, that the flight of an eider duck was at the 

 rate of 90 miles an hour. Sir George Cayley computes the 

 rate of flight, even of the common crow, at nearly 25 miles 

 an hour; and Spallanzani found that of the swallow com- 

 pleted about 92 miles, while he conjectures that the rapidity 

 of the swift is nearly three times greater. A falcon, which 

 belonged to Henry IV. of France, escaped from Fontainbleau, 

 and in 24 hours was found at Malta, a distance of 1350 miles; 

 a velocity nearly equal to 57 miles an hour, supposing the 

 falcon to have been upon the wing the whole time. But as 

 such birds never fly by night, and allowing the day to be at 

 the longest, his flight was perhaps equal to 75 miles an hour. 

 It is probable, however, that he neither had so many hours of 

 light in the twenty-four, to perform his journey, nor that lie 

 was retaken the moment of his arrival. But if we even re- 

 strict the migratory flight of birds to the rate of 50 miles an 

 hour, how easily can they perform their most extensive migra- 

 tions! and we know, in the case of woodcocks, and perhaps 

 all other migrating birds, that they in general take advantage 

 of a fair wind with which to perform their flights. This 

 breeze perhaps aids them at the rate of 30 or 40 miles an hour; 

 nay, with three times greater rapidity, even in a moderate 

 breeze, if we are to give credit to the statement of aerial nav- 

 igators, who seem to consider the rate of the motion of winds 

 as in general stated too low." If this be true, the movements 

 of birds in their migrations may be performed with little dif- 

 ficulty ; for even those that execute their journeys at one 



