35 



[Ctikt. IX, 



PARA. 25.1 



foi limited times on special occasions, as when a bird is 

 frightened by an enemy or when it is pouncing on its 

 prey. It may be added that "flex-gliding," as Dr. Hankin 

 calls it, is not necessarily by any means the most rapid 

 means of flight for all birds. Tlie Peregrine, at top speed, 

 flaps its wings in furious, incessant beats. The flight of 

 Duck is always of the flapping variety without gliding or 

 indulatioiis. This is because of the heaviness of their 

 "loading,'' a convenient formula used to measure and 

 compare the weiglit lifted by birds per unit of supporting 

 area. "*If" writes Hankin, "the total area of the two 

 wings taken together were found to be 10 sq. ft. and if the', 

 weiglit of the bird were 20 lbs., then the loading would be 

 2 lbs. per sq. feet." Where the tail is large (as it is not 

 in the Ducks), it should be included as well as the wings . 

 in the total supporting area. A comparison of the Duck 

 tribe in this matter with some other birds is interesting, 

 showing, as it does, that the Ducks have to lift a heavier 

 vviijoht even than the Vultures. 



Take it, however, as a basis of discussion that the 

 ordinary speed of the average-paced Duck, say when 

 flighting or not alarmed, is forty miles per hour. For 

 this speed the ammunition-makers lay down, for practical 

 purposes, an allowance of a foot for every five yards of 

 range, or eight feet at forty }ards. Now, in the cir- 

 cumstance specially considered in this book, viz., shooting 

 at birds driven from butt to butt by firing and kept away 

 from distant harbourage by bombing or other means, it 

 is obvious that a velocity much in advance of the average 

 40 miles an hour will often be attained. There is also 

 the possibility of a following wind from the " light breeze" 

 of 14 and the "steady breeze"" of 21, to the" gale " of 40 miles 

 per hour, to be reckoned with, the whole velocity of which 



* Reprinted from '•Animal Flight" by permission of lliffe and 

 fcions Limited. 



t From Maxim's "Natural and Artificial Flight," as quoted by 

 ]I;^iikiu. 



