BIRDS 



I6 5 



OK 



FIG. 307. POSITION OF VOCAL 

 CORDS (sir) OF MAMMAL AND BIRD. 



Question : Does a fowl ever croak after 

 its head and part of its neck are cut off? 

 Explain. 



or less, in proportion to its weight, than an animal that 

 lives on the ground ? Are the vocal cords of a bird 

 higher or lower in the wind- 

 pipe than those of a man? 

 (Fig. 307.) 



The heart of a bird, like a 

 man's heart, has four cham- 

 bers ; hence it keeps the 

 purified blood separate from 

 the impure blood. Since 

 pure blood reaches the or- 

 gans of a bird, oxidation is 

 more perfect than in the 

 body of any animals yet 

 studied. Birds have higher 

 temperature than any other class of animals whatsoever. 

 Tell how the jaws, tail, and wings of the fossil bird 

 Archaeopteryx differed from living birds (Fig. 290). 



SUGGESTIONS. In the field work, besides seeking the answers to 

 definite questions, pupils may be required to hand in a record of the 

 places and times of seeing a certain number of birds (20 to 40), with 

 the actions and features which made each distinguishable. Also, and 

 more important, each pupil should hand in a record of a careful and 

 thorough outdoor study of one common species (see below) as regards 

 habits, nesting, relation to environment, etc. 



Field Study of a Common Species. (For written report.) 

 Name of species. Haunts. Method of locomotion when not 

 flying. Flying (rate, sailing, accompanying sound if any, soaring). 



What is the food? How obtained? Association with birds of 

 its own species. Relation to birds of other species. 



Where does it build its nest? Why is such a situation selected? 

 Of what is the nest built? How is the material carried, and 

 how built into the nest? Does the bird's body fill the nest? 



Describe the eggs. Does the male bird ever sit or otherwise 

 assist female before hatching? Does it assist after hatching? 



