Care of Young and Nest. 



109 



and so is also the care with which they avoid any defilement of the nesting site. The use 

 of the excreta as food, however, is to be regarded in a different light. If it should be 

 proved that in the Robin, for instance, some individuals never eat the excreta, while others 

 as we know do, we should regard the action as an acquired habit. When the pellicle 

 breaks in the mouth, an accident which I have seen happen in the case of the Robin, t he- 

 bird is obliged to swallow a part in order to get rid of it. 



Much light is thrown on this 

 question by the behavior of the 

 Chestnut-sided Warblers, whose 

 habits will be referred to again in 

 the concluding chapter. Both sexes 

 in this case fed, brooded, and 

 cleaned the young and nest. The 

 male regularly removed the excreta 

 but was never seen to eat it. The 

 female on the contrary often ate of 

 it, and brooded so constantly that 

 she was obliged to leave the nest 

 to satisfy her own hunger. She 

 would often be back in half a minute, 

 having taken only a bite as it were. 

 \Vhen the female had received 

 the food which her mate sup- 

 plied and had seen it safely deliv- 

 ered, she would inspect, devour 

 everything which needed removal, 

 and then continue to brood. If a 

 sac should accidentally fall, she 

 would snap it off the ground, return 

 to the nest, and brood as before. 

 At other times when the male ap- 

 proached she would stand aside 

 and allow him to deliver the food 

 and make the inspection. Twice 

 I saw the male take a sac to carry 

 it away, and the female snatch it 



from him, swallow it, and settle down on the nest. Again another sac was torn asunder, 

 and each bird went off with a half in its bill. In a moment the female returned but 

 without bringing food, showing that she had been satisfying her own hunger. This not 

 only proves that the excreta is used as food but illustrates how the habit of eating it 

 may be forced upon a hungry brooding bird. 



Since digestion in the young is an imperfect process at best, it is easy to understand 

 how any kind of pre-digested or partly digested food might be acceptable in times of 

 stress when the staple article was not easy to procure. The fact that a bird only casually 

 devours a pellet or swallows one and removes another is easy to understand. It is a ques- 



Fig. 105. Serving a black cricket to a fledgling who has climbed to 

 the rim of the nest and is struggling to maintain his position. 



