ALARM-NOTES 31 



its elevated perch by the milvago-hawk, when, if it 

 had understood the warning cry of the foster-parent, 

 it would have dropped down into the bush or grass 

 and escaped ; but, as soon as the young cow-birds 

 are able to shift for themselves and begin to 

 associate with their own kind, their habits change, 

 and they become suspicious and wild like other 

 birds" (pp. tit. p. 89). 



It would seem that the alarm-cries of birds were 

 at an early period developed so as to induce silence 

 in the objects to which they were addressed. Mr. 

 Hudson, who has carefully considered this subject, 

 says : " When very young, and before their educa- 

 tion has well begun, if quietly approached or 

 touched, they open their bills and take food as 

 readily from a man as from a parent bird ; but if, 

 while being thus fed, the parent returns and emits 

 the warning-note, they instantly cease their hunger- 

 cries, close their gaping mouths, and crouch down 

 frightened in the nest. This fear caused by the 

 parent bird's warning-note begins to manifest itself 

 even before the young are hatched ; and my 

 observations on this point refer to several species in 

 three widely -separated orders. When the little 

 prisoner is hammering at its shell and uttering its 

 feeble peep, as if begging to be let out, if the 



