NO. I LOCOMOTOR MECHANISMS OF BIRDS — HARTMAN 33 



is customary. The greater the wing loading, the faster the bird must 

 fly to prevent stalling. A long, narrow, pointed, flat wing is faster than 

 a broad, curved one of the same area. Camber is greatest in slow fliers. 

 Short wings are for bursts of speed. Wing areas are larger than 

 absolutely necessary, especially in small birds, as can be shown in 

 partial molts of wing feathers. 



For sustained fast flying a low buoyancy index is best, while for 

 soaring and gliding a higher index is an advantage ( George and Nair 

 1952). Coturnix migrates considerable distances. Its aspect ratio is 

 2.15, its buoyancy index, 2.38, compared with a nonmigratory phasi- 

 anid, Colinus, whose aspect ratio is 1.74 and buoyancy index 2.6. 



Some birds are so equipped and so skilled that they have great 

 control. The sparrow hawk, the kingfisher, and the hummingbird can 

 hover, and the last mentioned can fly in any direction. The outer wing 

 serves as propeller, while the inner wing, like that of a plane, gives 

 "lift." In the hummingbird the wing is mostly propeller, giving great 

 maneuverability but less efficiency. While this is satisfactory for a 

 small bird, in a larger one greater efficiency is needed because weight 

 increases by three dimensions while lift increases by only two dimen- 

 sions (Storer, 1948). 



In general, as has been stated by others, the small birds have rela- 

 tively large, broad wings which give great maneuverability. This wing 

 size is usually accompanied by tails that assist materially in quick 

 change of direction or in landing. Small birds take off essentially by 

 the same process as that used in free flight, the functions of lift and 

 propulsion being common to a wing undifferentiated on the long axis 

 and unadapted for kite-surface action (Demoll, 1930). 



If the various species were arranged according to the size of the 

 most important flight muscles (pectoralis superficialis plus supra- 

 coracoideus) we find that other values bear no relation to this arrange- 

 ment. In table 5 (p. 91) typical examples are shown. Those species 

 with 30 percent pectoralis plus supracoracoideus possessed wings rang- 

 ing from 3.67 to 0.95 cm. 2 per gram (buoyancy index, 3.31 to 2.91), 

 glide areas from 6.71 to 1.16 cm. 2 per gram, and hearts from 2.10 to 

 0.20 percent of the body. What does this indicate? The small wing 

 would require a more rapid beat for the same performance. Large 

 leg muscles suggest greater activity on the ground. The behavior of 

 the birds listed bears this out. The hummingbird is a powerful sus- 

 tained flier with little use for his legs. The tinamou is a ground bird 

 and an explosive flier that spends little time in the air. 



Consider the three birds with the smallest pectoralis plus supra- 



