The Audubon Societies 6t 



it is too long and complicated a story for us, as yet, to follow through, we can 

 learn it bit by bit, as we study more and more into the subject of the bird's 

 structure. 



When we come to the circulatory system of the bird, which goes hand in 

 hand with its digestive system, the same economy of apparatus is found, 

 without loss of thoroughness. In birds, the blood is kept pure and moving rapidly, 

 especially to the relatively huge flight muscles, for it is very necessary to have 

 constantly on hand fresh, air-purified blood in sufficient quantity to aid in pro- 

 ducing the energy which must be ceaselessly transmitted into heat and motion 

 and other uses. 



If you could look at the heart of a fish and the heart of a reptile and the 

 heart of a bird, with all the arteries, veins, and tiny tubes called capillaries 

 that go into them, you would have one of Nature's interesting stories before 

 you. It is something to look forward to as you study more, and though it is in 

 places difiicult to discover all the reasons for the different ways in which the 

 blood of fishes, reptiles, and birds circulates, there is always a reason and it can 

 be found out by careful study. 



A point to emphasize now is the practical working of the bird's internal 

 machinery and, as already said, this centers around food. With the bird, it is 

 always food and more food. In fact, food is the mainspring of all life, and this 

 we are coming to realize in these days of stress and war, as never before in this 

 generation. If the food-relations of different races and classes of men could be 

 more equally adjusted, it is probable that the rnajor woes of mankind would dis- 

 appear, for the demand for food and for more food is constantly upper- 

 most in our daily life, with the increase and spread of population. Birds have 

 then a problem quite like our own to face, which should lend interest and 

 sympathy to our study of and relations with them. It is a modern philosopher 

 who says: "The haps and mishaps of the hungry make up natural history." 



In this year of 191 8 we are all called upon to conserve and to produce more 

 food than ever before. The birds can help us if we will help them. One way 

 to take hold of this question of the food-relations of birds and man is to classify 

 the different kinds of food and food-habits — first, of birds and, second, of man. 

 A simple scheme with reference to birds, as follows, may be suggestive to you, 

 in making out a similar scheme for man: 



I 



1. Fish-eating birds. 



2. Vegetarian birds. Weed-seed, fruit, grass and tender weeds. 



3. Insectivorous birds. 



4. Carnivorous birds. 



5. Birds which eat more than one kind of food. 



6. Birds which vary their food during the different seasons of the year. 



7. Birds which eat carrion or are of scavenger habit. 



8. Birds which feed in flocks and reasons for the kinds of damage they may un- 

 wittingly do to crops. 



