INSTINCT AND INTELLIGENCE IN BIRDS 547 



complished, the female returned with an insect, and resumed her brood- 

 ing again. 



The instincts of the parent and young are of the lock and key order. 

 Each acts as a stimulus to the other, and the reward of satisfaction to 

 the child is no greater than that of pleasure to the parent. The co- 

 ordinated instinctive responses of the young begin in many of the 

 precocious birds, like the great herring gull, before birth. The egg is 

 starred and pipped, and the bill of the little bird is seen, and its call 

 note heard, for several hours before the shell is cracked open. The 



Fig. 9. Goldfinch feeding Seed-pap by Regurgitation. Note uniformity of response. 



split may occur with a certain degree of uniformity in the direction of 

 the minor axis of the egg, thus dividing it into two equal or unequal 

 parts, and when the chick crawls out it leaves, besides the shell and its 

 membrane, the allantois, and what looks like a residue of the albumen. 

 The shells which now encumber the nest are carefully removed by some 

 birds, and dropped, presumably at some distance away, while in others 

 they are brushed aside, or crushed by the brooding bird and receive 

 no further attention. This removal of the shells so common in the 

 Passeres and other orders, must be attributed to the cleaning instinct, 

 and I have noticed that in the cuckoo, which removes the shells of the 

 first two or three young to hatch in succession, is apt to leave those of 

 the last when the cleaning instinct is on the wane. The allantois is 

 sometimes picked out of the shell and eaten, as has been seen in the 

 case of the gull. 



