30 



CIVIC BIOLOGY 



with neighboring districts in which no such provisions are 

 made ? A\"hat is the practical value of such work as shown 

 by your account of insect injury ? of losses caused by birds ? 

 Other important lines of bird work relate to destruction of 

 weed seeds and the control-by owls, hawks, and slnikes of nox- 

 ious mammals, — mice, moles, rats, gophers, etc. Keep these 

 matters in mmd throughout the year while domg the field work. 



Fig, 12. Bird house for study of home life ; windowpane is back wall of house 



Photograph by the author 



The birds in your district will change during different sea- 

 sons. During the fall migration the " summer residents " will 

 leave for the south, and many species whose breeding range is 

 farther north will migrate through the territory. These species 

 may be designated as ''transient visitants." They migrate by 

 us to the northward in the spring and southward in the fall. 

 After settled cold weather begins there will be left the '' per- 

 manent residents," — about thirty-six species for the latitude 



