THE VELOCITIES OF MIGRATORY BIRDS. 243 



The fact that a head wind stops migration, and that they are 

 seeing retarded birds, seems to have eluded the understanding of 

 Gatke and others. 



The "feather-ruffling" aspect is also based on the mis- 

 interpretation of a common observation. Such birds as Lap- 

 wings, in rough weather, constantly stand head to wind. If 

 they happen to turn, their feathers are ruffled. A not too robust 

 philosophy has led many people to say that exactly the same 

 thing happens if the bird is flying, and no longer on the ground. 

 The equally absurd if less inexcusable belief that a flying bird, 

 if it is to maintain its altitude, must move at a greater velocity than 

 the ivind if flying in the same direction is based on the fact that 

 a cyclist, for example, riding at twelve miles an hour in the 

 teeth of a wind of the same velocity, rushes through the air at 

 the speed of twenty-four miles an hour. Biding in the opposite 

 direction, of course, he is in effect in a calm. 



A bird must maintain a certain speed to keep itself in the 

 air — let us say twelve miles an hour. The idea is that flying 

 tail to wind (velocity twelve miles per hour) it finds itself in a 

 calm, and " the air ceases to support it ; it falls to the ground." 

 The theory is a good example of its kind — unsupported by 

 observations, and directly opposed to four or five well-known 

 natural laws ; it is, of course, merely a logical outcome of the 

 superstition of head winds. The actual " facts " have not been 

 observed, but evolved in the mind of the writer, in agreement 

 with his theory. There is no such thing as wind, as we know it, 

 to the flying bird. It is travelling in a medium that happens to 

 be moving bodily over the surface of the earth. The man feels 

 the same medium rushing past him. 



The point is : Can a bird fly tail to wind, or head to wind ? 

 What observations are available ? On many occasions I have 

 seen birds unable to travel head to wind, and I have also seen 

 birds moving at great speed tail to wind. On March 6th, 1909, a 

 blizzard of unusual severity raged over the greater part of 

 England. I happened to be at that time on the Lincolnshire 

 coast, and, notwithstanding an unparalleled state of bodily dis- 

 comfort, I contrived to carry out some experiments on the birds. 

 The wind, at the sea-level, was blowing, so far as I could estimate 

 it without instruments, at not less than fifty miles per hour. 



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