n6 NATURE-STUDY 



watch the development of the nestlings. At first ugly and 

 nearly naked, they become covered with down, and then 

 later the real feathers appear, first on the shoulders, wings, 

 and tail, and later on the rest of the body. The colors of the 

 young, even when fully fledged, are not quite like those of 

 the old birds, are less distinct in marking and less intense. 



Watch the old birds feed the young. They seem almost 

 always hungry, and keep their parents very busy, bring- 

 ing worms, insects, fruit, 

 grain, etc. Professor Tread- 

 well records that a young 

 robin requires its own 

 weight of insects daily. 

 The parents have been 

 timed to carry food as 

 often as once a minute to 

 FIG. 21. Young Grosbeaks. the young. The infant diet, 



even of seed-eaters like the sparrows, is at first almost wholly 

 insects- and worms. After leaving the nest the young still 

 receive some care from their parents. The robins, blue- 

 jays, grosbeaks, and sparrows may be seen in the yards and 

 on the lawns, feeding the big babies that have left the nest 

 and can fly almost as well as the old ones. 



Migration 



Most of our birds migrate to milder climates as the cold 

 weather of autumn approaches. The increasing coolness of 

 the weather and the decreasing food supply, especially in- 

 sects, are probably the chief reasons for migration, though 

 there are probably other influences that impel the birds to 

 take up their yearly pilgrimages. Migration habits are in- 



