2 Wild Birds 



I will now give the reader a less enigmatical account of the 

 method, first considering its psychological basis or the scientific 

 principles on which it rests, and then recording in a separate 



Fig. i. Tent in front of Cedar-bird's nest, shown in its original position 

 in Fig. 18. One of the birds is feeding its young. 



chapter, as practical examples of its working, the exact history 

 of a few of the cases in which it has been applied. 



The method in use depends mainly upon two conditions : 



(1) The control of the nesting site, and 



(2) The concealment of the observer. 



By nesting site is meant the nest and its immediate sur- 



