INTRODUCTORY xi 
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, waxwings, 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. 
Cuicaco, January 1, 1904. 
