LIFE AXD BEHAVIOR OF THE CUCKOO 
173 
extend them at either end of the reproductive c^'cle. To the diffi- 
culty of obtaining full and satisfactory records of the free behavior 
of birds is doubtless due the paucity which exists. To illustrate: 
before the writer's work, represented in a small part by the present 
paper, was undertaken, over ten years ago, the cyclical instincts 
of birds had never been properly studied and analyzed in our com- 
monest species. (Especiall}^ as to the terms nos. 3-6 as given 
in section 5). The field was practically unexplored by both 
biologist and psychologist. Such coirunon stereotyped behavior 
as inspection of nest, throat-testing, and shielding, had never been 
described, but little was known on the subject of nest-building 
as distinguished from description of the completed structure. 
With the exception of a few notes on young birds held in cap- 
tivity, these observations have all been made in the field, at North- 
field, New Hampshire, in July and August, 1908 and 1909. IMy 
object being to study the correlative instincts of the young and 
adult in relation to all that could be learned about them in a 
natural environment, I have followed my usual custom of going 
out to the birds, instead of taking them into the laboratory. The 
facts which the laboratory can be made to yield are invaluable, 
but they belong to a different class from those for which we are 
now mainly in search, behavior under the usual or normal condi- 
tions. 
Knowing that the conditions for the study of free behavior in 
the field, especially with birds where the young and adults are 
held for a considerable time to a fixed point by the nest, can be 
made to yield far more to biology and psychology than has yet 
been realized, it seems to me best to follow such methods whenever 
practicable, and so long as any new or important result is to be 
attained. 
My general methods of study have been fully described else- 
where,^ and I will now only add that aside from making an}^ of the 
weighings or measurements which may be needed, and testing 
the reactions of the young under various conditions and at stated 
5 The home life of wild birds; A new method of the study and photography 
of birds. Revised ed. New York, 1905. 
