CAROLINA DUCK 63 



nest and flew directly away. But if, especially at night, the observer crept up quietly 

 and then scratched the trunk in imitation of a climbing beast, the duck dropped into 

 the water close by and went through the familiar broken-wing tactics, endeavoring 

 to entice the supposed enemy away. 



Heinroth found that in spite of the great heat which is generated in some of the 

 nesting hollows, no harm ever came to the female or to the eggs. Linden (1882) 

 noted that the young Carolina Ducks were kept in the nest for twenty-four hours 

 after hatching, and Heinroth 's observations, as well as Dixon's, bear out this state- 

 ment. Heinroth saw the mother draw considerable oil from the tail gland and rub it 

 on her underside soon after the young were hatched. She repeated this action at 

 frequent intervals while in the box with the young, but she was never seen to do this 

 while incubating. This appears to be Nature's method of automatically water- 

 proofing the young. A point of great interest with this duck is the high percentage 

 of infertile eggs, nearly always the case in captive stocks. I always supposed this to 

 be a result of unnatural conditions, but Dixon's studies on wild birds showed nearly 

 fifty per cent which did not hatch. Now this is just about the proportion of sterility 

 found in captive birds. It is rare to have over seventy per cent fertile in one season, 

 and this is very much higher than the average proportion. It would seem that this 

 unusual amount of sterility is characteristic of the species. 



So many loose statements and so much hearsay evidence concerning the methods 

 by which the young are transported to the ground or water have been allowed to ac- 

 cumulate in the literature, that it is impossible as well as futile to consider them all. 

 The first careful set of observations on this much-disputed point are, again, those of 

 Heinroth. About quarter of seven in the morning of the day after the hatching the 

 mother duck began to look out of the nest-opening and shortly afterward flew away 

 directly to the ground and not in her usual direction. The note which she uttered 

 was the well-known (but somewhat modified) tetetetet. "Immediately after one of 

 the ducklings appeared in the entrance, and a moment later I heard it drop on the 

 roof in front of me, and then two more followed, then a few more, and in the lapse of 

 about three quarters of a minute the nest was empty." There is an excellent photo- 

 graph accompanying Heinroth's paper, showing two of the young about to jump 

 from the nest-hole. Actually the little ones stood in the entrance for a moment and 

 then took a powerful up and out jump, shooting from the box as if thrown by some 

 invisible power. They all landed safely either on the roof or on the ground, and the 

 old one immediately set out for the pond with those she had collected, paying no 

 attention to three who were left behind owing to various mishaps. At other times 

 Heinroth observed the evacuation of the nest by the young and sometimes several 

 minutes elapsed between the time the mother left the nest and the young jumped. 

 Among the most remarkable adaptations are the needle-like claws with which the 

 young are provided and which enable them to climb up perpendicular or even over- 



