428 



REPTILES AND BIRDS. 



the space of twelve hours, it follows that they must have travelled 

 the above space at the rate of a mile a minute. One of these birds, 

 if able to keep up this velocity, could visit the European continent 

 (from America) in less than three days." 



It is not for the purpose of seeking a warmer climate that they 



Fig. 163.— Migratory Pigeons. 



undertake their journeys, but to procure food when the acorns 

 become scarce in the woods which they inhabit. Their migrations, 

 consequently, are irregular as to date. Looking at the innumerable 

 and closely packed masses of passenger Pigeons which take part in 

 these voyages confuses the mind. Audubon one day endeavoured 

 to count the flocks which passed above him in one hour. He counted 

 163 in twenty minutes, but he was soon obliged to give up, the 



