INSTINCT AND INTELLIGENCE IN BIRDS 



539 



see an insect which has been inserted in the mouth of a nestling, with- 

 drawn, minced with the bill, and offered again. When behavior is free the 

 return to the nest (&), is prompt and direct, but birds will frequently 

 pause at some point near by and look about as if for assurance. The 

 black-billed cuckoo if timid or suspicious, will sometimes stand on 

 such a perch with insect in bill for five or ten minutes without uttering 

 a sound, but occasionally pumping its tail, stretching its head and 

 looking cautiously around, or again it will remain perfectly quiet like a 

 statuette. The actual path which is now taken to the nest is eventually 



Fig. 3. Robin " taking aim." After photograph by John B. Parker. 



determined by habit. The bird flies to a certain branch, grasps certain 

 twigs, before it finally lands on a certain part of the nest itself. Then 

 usually follows a pause as the bird straightens up and stands over her 

 young. If the mate is brooding, as is likely to be the case in bad 

 weather, a call-note is sometimes given by the visiting bird, when the 

 sitter promptly retires. This note is often heard in the absence of the 

 mate, when it serves as a stimulus to the young. Further the sitter, if 

 a cuckoo, always detects the approach of the visiting bird by hearing, 

 if not by sight, so that the whole family is practically never seen to- 

 gether at the nest, contrary to what often happens with gulls, robins, 

 cedar-birds, kingbirds, or some of the warblers. The young detect the 

 approach of the parent by sight or sound, or by the vibration imparted 



