BIRDS 



171 



tralia and the United States than in Europe, because they 

 left behind them their native enemies and their new ene- 

 mies (crows, jays, shrikes, etc.) have not yet developed, to 

 a sufficient extent, the habit of preying upon them. Nature 

 will, perhaps, after a long time, restore the equilibrium 

 destroyed by presumptuous man. 



Protection of Birds. — 1. Leave as many trees and bushes 

 standing as possible. Plant trees, encourage bushes. 



2. Do not keep a cat. A mouse trap is more useful than 

 a cat. A tax should be imposed upon owners of cats. 



3. Make a bird house and place on a pole; remove 

 bark from pole that cats may not climb it, or put a broad 

 band of tin around the pole. 



4. Scatter food in winter. In dry regions and in hot 

 weather keep a shallow tin vessel containing water on the 

 roof of an outhouse, or out-of-the-way place for shy birds. 



5. Do not wear feathers obtained by the killing of birds. 

 What feathers are not so obtained ? 



6. Report all violators of laws for protection of birds. 



7. Destroy English sparrows. 



Migration. — Many birds, in fact most birds, migrate to 

 warmer climates to spend the winter. Naturalists were 

 once content to speak of the migra- 

 tion of birds as a wonderful instinct, 

 and made no attempt 

 to explain it. As 

 have the warmest covering 

 all animals, the winter mi- 

 gration is not for the pur- 

 pose of escaping the cold ; it 

 is probably to escape starva- 

 tion, because in cold countries food is largely hidden by 

 snow in winter. On the other hand, if the birds remained 



Fig. 315. — Great Blue Heron. 

 In flight, balancing with legs. 



