230 THE STRUCTURE AND LIFE OF BIRDS cuap. 
Flight in Troops. 
The formations adopted by birds when flying in 
troops are very interesting, but unfortunately not much 
is known of the subject. A wedge shape, the point 
Fic. 63 (after D’Esterno partly). 
Ducks in formations for troop-flying. 
The arrows in 1 and 2 represent the direction of the wind. In 1 the wash passes 
between those to leeward ; in 2 the leeward line is too far off to feel it. In 3 (wind 
ahead or aft or none), travelling each along his own line, they escape the wash and so 
also in V-formation. 
leading, is the favourite, certainly among most of the 
great water birds such as swans, cranes, and pelicans 
(see Fig. 63). Whatever the formation, the object is 
not that those in front may break the resistance of the 
air for the benefit of those behind them. A bicyclist, 
driving as he does a mass of air before him, gives 
