CLIFF-DWELLERS 25 



ish birds by the fact that they are more varied in 

 colour than those of any other species. They range 

 from light pink to pale green. The female bird 

 lays but one egg at a time, and, like the mother 

 of an only child, she bestows great attention upon 

 it. Unlike all other birds she refuses to trust this 

 precious and only treasure in a nest, but holds it 

 between her legs as she sits in her chosen burrow. 

 These birds are fast becoming rare. 



At Starved Rock, Illinois, a few years ago, there 

 was a most remarkable sight. A number of scien- 

 tists. Dr. Jesse M. Greenman, Mr. O. E. Lansing, 

 and myself were collecting plants for Field's Mu- 

 seum of Natural History, when we came to this 

 wonderful place. An immense rock, covered with 

 mavellpus pine trees, rose-bushes, and vines, nearly 

 a hundred feet high, stood by the side of the river. 

 Swallows were flying in and out of the sides of the 

 rock like bees out of a hive ; for the rock was liter- 

 ally covered with mud nests glued to the steep 

 walls. It was a city indeed of cave-dwellers out of 

 the reach of man I 



The strangest and most human-like habits of 

 clifp-dwellers, especially the swallows, is the burial 

 of their dead. If a swallow dies in its cave, the 

 other bird inhabitants wall up the nest, thus chang- 

 ing it into a hermetically sealed sepulchre. Only 



