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THE POPULAR SCIENCE MONTHLY 



It would be safe to affirm that the cuckoo or the cedarbird which 

 we happened to be watching, would in the course of time come to a 

 certain branch, look about, advance to the nest along a certain path, 

 marked out previously by habit, test the throat of one of the eager 

 young, watch for the swallowing reaction, inspect and take the sac, if 

 forthcoming, in the bill, but here no one could say whether the sac 

 would be borne away, and the bird return thereafter with food, or 

 whether it would be eaten, and the bird remain at the nest to brood. 

 Here association and other elements seem to enter. My records for the 

 cuckoo show that the brooding intervals, as to their length and fre- 



Fig. 8. Cuckoo placing Food in Throat ("testing" the throat) ; wings of 

 nestling at rest. One bird only receives food. 



quency, seem to depend upon the intensity of the light and the activity 

 of the male. During the early period of nest-life many birds brood 

 through the night, but at intervals only during the day. When the 

 sun becomes suddenly obscured with dense clouds, or it grows dark 

 with the approach of rain, brooding is likely to begin, and if the male 

 ceases to bring food, the brooding intervals are prolonged. Thus, 

 during a heavy rain storm I have known the black-billed cuckoo to 

 brood for the space of one hour and forty minutes, and only retire at 

 last at the approach of her mate with food. After his task was ac- 



