482 VERTEBRATE LIFE AND ORGANIZATION 



Sparrow (perching 



Jacana, 



(walKin^ on floatm^ plants) 



"S.vs<v 



Woodpedicer 

 (graspmg) 



Duclc ^^ 



Pheasant 



(walking, 

 scratching)/ 



Figure 24.10. Adaptations of the feet of birds. 



food, both plant and animal, but many birds have become specialists, 

 and have evolved adaptations for utilizing particular types of food. 

 Their bills are modified accordingly, and one can often tell from this 

 alone the nature of their food and how they get it (Fig. 38.1). Finches 

 have short, heavy bills well suited for picking up and breaking open 

 seeds. The hooked beak of hawks is ideal for tearing apart small animals, 

 which they have seized with their powerful talons. Herons use their long, 

 sharp bills for spearing fish and frogs, which they deftly flip into their 

 mouths (Fig. 24.9). The length and shape of hummingbirds' bills are 

 correlated with the structure of the flowers from which they extract 

 nectar. Whippoorwills and swallows fly about in the evening catching 

 insects with their gaping mouths. Bristle-like feathers at the base of the 

 bill help them to catch their prey. When feeding, the skimmer flies just 

 above the ocean with its elongated lower jaw skimming the surface. Any 

 fish or other organisms that are hit are flicked into its open mouth. The 

 woodcock's long and sensitive bill is adapted for probing for worms in 

 the soft ground. The woodcock can open the tip of its bill slightly to 

 grasp a worm without opening the rest of the mouth! 



Support and Locomotion. Flight in its various forms is, of course, 

 an important means of bird locomotion. When not flying, most birds 

 support themselves and move about on their hind legs. The foot has 

 undergone a variety of modifications as the bird has become adapted to 

 special modes of life (Fig. 24.10). The foot and toes become particularly 

 sturdy in ground-dwelling species, and the power of grasping is espe- 

 cially well developed in such perching specialists as our song birds. In 



