I6 Wild Birds 



with others we must wait until the young are from four to nine 

 days old. It is all a question of the strength of the parental 

 instinct, and this varies between wide limits in differ- 

 When to ent S p ec ies, and very considerably between different 

 change the individuals ' From the nature of the case there can be 

 :mg no infallible rule. If we know little of the habits of the 

 birds in question, it is safest to wait until the seventh to the 

 ninth day after the young are hatched, or when in many passerine 



Fig. g. Outdoor Observatory for the Study of Wild Birds complete, 

 showing the observation tent, the nesting trunk (in this case belonging 

 to the House Wren) mounted on a pivot and surrounded by the protective 

 wire net, with white photographic screen at back. The running series of 

 Wren pictures fFigs. 16-30) were made at this nest, Northfield, N. H., 

 July, 1901. 



birds, as Robins, Orioles, and Waxwings, the feather-shafts of 

 the wing-quills begin to appear in the young, or, better, when 

 they project from one quarter to one half inch beyond the 

 feather-tubes. At this period the parental instinct is reaching 

 its maximum, and, what is equally important, the sense of fear 

 has not appeared in the young. 



When we try to formulate a rule, however, we at once en- 

 counter numerous exceptions. Thus in Cuckoos the feathers 



