344 



PRACTICAL ZOOLOGY 



FIG. 222. The bank of a stream showing the entrances of a kingfisher's tun- 

 nel at the left and that of a bank swallow at the right. (Photo, by Hegner.) 



Birds preen themselves by pressing a drop of oil from the oil 

 gland, which lies just above the tail , and spreading it over their 



FIG. 223. Bank swallow on its nest at the end of a tunnel in the 

 bank of a stream. (Photo, by Hegner.) 



