148 NATURE STUDY- BY GRADES 



What reasons can be given for the migration of birds ? Let 

 the pupils suggest and discuss: (a) the weather ; (b) the food 

 supply ; (c) the lack of foliage, shelter, etc. ; (d) their powers 

 of locomotion as compared with animals which do not mi- 

 grate; (e) their intelligence compared with others; (/) the 

 dangers and fatalities in making the flight; and any other 

 conditions that will make clearer the subject of the migration 

 of birds. Tell stories illustrative of the same. 



It is said that less than 25 per cent of the birds that leave 

 us ever return. It might be interesting to do a little number 

 work in this connection. Suppose the life of a robin is ten 

 years and that a pair will produce ten young each year. If 

 none were killed, find how many there would be at the end 

 of each year say, for five years ; for ten years, etc. 



Do any animals besides birds migrate ? Discuss in a simi- 

 lar way these animals and their reasons and times for migrat- 

 ing; the distances they go and the differences in conditions 

 that they encounter. 



NOTE. Most animals that roam in herds move from one feeding 

 ground to another at somewhat regular intervals. The deep snows of 

 winter drive many animals from the mountains into the warmer valleys. 

 Many fishes swim upstream at certain seasons to spawn. 



LESSON XXIII 

 METAMORPHIC ANIMALS 



Notice the disappearance of butterflies and moths. Where 

 do they and other insects live during the winter? What is 

 their food? Is there enough during the winter? If food 

 were abundant, could they stand the rigors of winter weather ? 

 Do they migrate as the birds? Are they capable of making 

 so long and dangerous a journey ? 



