INTRODUCTORY xiii 



the nest. Out of one hundred and eighty cases recorded 

 by the author, in every instance where the young were 

 hatched in a naked or semi-naked condition they were 

 fed in this manner for at least three days. In some 

 instances the food was digested, wholly or in part ; 

 in others it was probably swallowed merely for con- 

 venience in carrying, and was regurgitated in an un- 

 digested condition. There seemed to be no definite 

 relation between the duration of the period of regurgi- 

 tative feeding and the length of time required for 

 the full development of the fledgeling. Young vul- 

 tures were fed in this way for ten days, and stayed in 

 the nest nine weeks. Young robins received their 

 food by this process three, occasionally four, days, 

 and usually took flight on the fifteenth day. Hum- 

 ming-birds, swallows, and a few others are fed by 

 regurgitation so long as they remain in the nest. 

 Goldfinches, wax wings, and others are nourished in 

 this way, with an occasional meal of raw food, until 

 they are ready to fly. The list is a long one, and as 

 most if not all of these instances are mentioned in 

 their individual biographies, given in this volume, 

 they need not be cited here. Scientists have long 

 known that pigeons, doves, and humming-birds feed 

 their young in this manner, and the discovery that 

 most species do likewise need cause no surprise. 



Irene Grosvenor Wheelock. 



Chicago, .laimarv 1, 1904. 



