BIRDS OF THE REGION 145 



picked off and fed to them by the parents. However, 

 most of the owl story was read at the base of the cliff 

 in pellets of fur and bones regurgitated from the 

 stomachs of the old owls, and by thousands of bones of 

 small animals scattered over the ground from old, dis- 

 integrated pellets. As is well known, such small animals 

 as mice and rats are swallowed whole by owls, while 

 larger game up to the size of rabbits is torn apart and 

 bolted in coarse pieces, — fur, feathers, bones, and all. 

 The whole is retained in the stomach until the food 

 part is digested, when the remaining felted mass of fur, 

 feathers, and bones is gulped up and thrown from the 

 owls ' mouths. In course of time these pellets (Fig. 55) 

 drop apart and leave bits of bones scattered over the 

 surface of the ground. Most of the bones were easily 

 recognized as having belonged to the small mammals of 

 the region, but some, requiring more careful study and 

 comparison, were brought back, and were identified by 

 Remington Kellogg of the United States Biological 

 Survey. 



Examination proved there was much similarity in 

 the pellets and bones from different caves and cliffs, 

 the principal variation depending upon local abundance 

 of the various kinds of prey eaten. The main local 

 differences consisted of considerable numbers of bones 

 of the guano bats in the Carlsbad Cave, the bones of 

 white-throated swifts in the Bighorn Cave, and the bones 

 of ducks and fish near the Pecos River. The bones 

 not only indicated the regular food of the owls, but 

 also represented practically the whole rodent and small 

 animal population of the region. By far the greater 



