54 ANIMALS AT WORK AND PLA Y 



infer that they have some strong motive for observing 

 such an order. The old-fashioned explanation, that 

 by advancing in a wedge the front bird acted as a 

 kind of pioneer, to break the force of the wind, is, 

 however, probably the exact reverse of the truth. 

 Wind, in moderation, is almost a necessity to the 

 sustained flight of birds, and the probable object of 

 the wedge-formation when advancing against the 

 wind is, that each bird avoids the 'wake' of its 

 neighbour, while at the same time the flock has a 

 leader. When the wind blows on the side of the 

 V, it has been noticed that one limb is generally 

 much longer than the other, or that the birds forming 

 one limb occupy positions which coincide with the 

 spaces between the birds on the windward side, and 

 are thus exposed to the wind current. But often 

 with a strong side wind the wedge formation is 

 abandoned altogether, and the ducks fly in single 

 file, though the ' distances ' are always accurately 

 kept. If these distances could be measured, they 

 would probably be found to bear some relation to 

 the space required by the particular species to make 

 a turn, more or less complete, to either side. The 

 sudden changes in the method of flight, from steady 

 beats of the wing to gliding or sailing, which takes 

 place with such wonderful uniformity of time and 

 action in the flight of flocks of starlings or plovers, 



