Fig. 307.—Position of Vocal Cords (str) of Mammal and Bird.
Question: Does a fowl ever croak after its head and part of its neck are cut off? Explain.
The heart of a bird, like a man’s heart, has four chambers; hence it keeps the purified blood separate from the impure blood. Since pure blood reaches the organs 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, the tail, and the wings of the fossil bird Archæopteryx 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 the times of seeing a certain number of birds (20–40) 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? How long is taken to lay a sitting of eggs? How long before the birds are hatched? When hatched are they helpless? Blind? Feathered? (Figs. [301], [302].) Do the nestlings require much food? How many times in an hour is food brought? How distributed? Even if the old birds sometimes eat fruit do they take fruit to the young? What do they feed to the young? How long before they leave the nest? Do the parents try to teach them to fly? Do the parents care for them after the nest is left? What songs or calls has the bird?
Fig. 308.—European Tomtit’s Nest.
What are the advantages of its shape?