NO. I LOCOMOTOR MECHANISMS OF BIRDS — HARTMAN 7 



flight muscles were little more than one-tenth the value of those of 

 the adult (2.28 percent). Likewise, an immature male Podilymbus 

 podiceps that had attained the weight of the adult (450 g.) possessed 

 flight muscles (7.58 percent) somewhat less than those of the adult, 

 while the legs were the size of those of the adult (18.9 percent). The 

 wing feathers were just emerging. 



Ciconiidae. — The wood ibis springs powerfully into the air and 

 flies higher and higher until almost out of sight, when he sails grace- 

 fully on motionless wings in wide circles. His flight muscles are 

 somewhat larger (27 percent of body) and his wings narrower (aspect 

 ratio, 2.85) than in most herons, but his legs are about the same size 

 (10.9 percent). 



Threskiornithidae. — The white ibis walks and climbs nimbly and 

 swims well. He flies with strong, rapid strokes, varied with occasional 

 periods of sailing. There is nothing unusual about his measurements. 



Anatidae. — Both the pintail {Anas acuta) and blue-winged teal 

 {Anas discors) are fast fliers with fairly large hearts (1.23 and 

 1. 1 5 percent respectively) and large flight muscles (31.36 and 29.2 per- 

 cent). They spring upward from the water and get underway at 

 once. The whistling of the teal's wings is probably due to the rapid 

 wing beats, since the wings are small for the weight (buoyancy index, 

 2.84). The lesser scaup {Aythya affinis), a rather laborious but steady 

 flier, has a buoyancy index of 2.62. Its heart is smaller than that of 

 Oxyura dominica (P<o.05) and Anas acuta (P<o.oi). The heart 

 of Cairina, in the domesticated form, is smallest of all. The flight 

 muscles of the male Cairina are smaller (P<o.oi) than those of the 

 female, while the reverse is true for the legs. The supracoracoideus in 

 ducks is about one-third that of the "rest" group. Cairina possesses 

 the largest legs of all ducks studied. 



Cathartidae. — The flight of Coragyps is inferior to that of Ca- 

 thartes. He has smaller wings (P<o.oi) and flight muscles (P<o.o5) 

 a larger heart and legs (P<o.oi,), and broader wings. Differences 

 are also shown between Panama and Florida vultures. The hearts of 

 Florida Coragyps (P<o.o5) and Cathartes (P<o.oi) are larger than 

 those of the Panama species. 



Accipitridae. — Among the hawks, Elanoides is unsurpassed in 

 beautiful maneuverings. With his long wings (aspect ratio, 3.40) 

 and forked tail he soars aloft to sport among the clouds. The speedy 

 accipiters fly by a series of quick flappings followed by short periods 

 of rapid sailing. In contrast the Buteo flight is heavy but powerful 

 and graceful. Buteogallus anthracinus is similar in flight. 



