HOW THE BIRDS KNOW 333 



that they can not see well in a fog so they call to 

 each other in order to keep together. Since we 

 know that birds unerringly cross miles of water at 

 a height from two to three miles and find the loca- 

 tion suitable for them, it seems that the old theory 

 of landmarks can well be abandoned, while there 

 is no question of the figures as to height given by 

 astronomical observers, who are the most skilled 

 mathematicians in all the world. 



When it comes to the speed at which birds fly, 

 it appeals to me that the scientists of former days 

 made great mistakes. In a sustained flight at a 

 fair height a carrier pigeon will average thirty-six 

 miles an hour. It seems to me that the flight of a 

 carrier pigeon, a bird of strong wing and unerring 

 sense of direction, might very well be taken as a 

 basis of computing the average flight of birds, at 

 least of the pigeon and plover families. It may 

 also be recalled that when riding on a railroad train, 

 going at a speed of about forty miles an hour we 

 often leave behind birds flying in the same direc- 

 tion. Of course such birds would not be in migra- 

 tion and so would not be flying so swiftly nor surely 

 in one direction as at that time, but such a test 

 would be of some value in determining the average 

 speed of flight. So great an authority as Herr 

 Gatke estimates that birds in migration are capable 

 of a speed of four English mfles to the minute. 

 This seems perfectly incredible, as at that rate a bird 

 would total two hundred and forty miles an hour. 



