usually with, feathers more or less erected, especially on the 

 crown. The female, on the other hand, was very sleek and well 

 groomed, and displayed very little fear, or scarcely even concern. 

 We soon discovered also that the hind toe was lacking on the 

 right foot of the female. There was also a recognizable differ- 

 ence in the shape of the head in the two individuals ; the crown 

 of the male being noticeably higher, i. e., above the level of the 

 eyes, while the crown of the female was low and flat. 



No blind was erected for the study of the nest. By depress- 

 ing the limb slightly, and anchoring it, the nest was low enough, 

 to be observed by the person seated. A camp chair was placed 

 beside the nest, first at a dist^ance of four or five feet ; but within 

 an hour or so the chair was moved so close that the observer could 

 touch the nest, and further observations were made from thisi 

 position, mth no attempt whatever at concealment. 



While the work of the parents went along in a fairly regular 

 manner, there may be some question as to whether their behavior 

 was perfectly normal, or as nearly so as it might have been with 

 tke observer concealed in a blind. The parental instincts are so 

 strong at this period that the fear instinct is, to a greater or less 

 extent, modified. However, if there was any modification of 

 normal behavior on this account, it probably did not in any way 

 alter the character of the food brought to the young birds. On 

 one occasion prior to the commencement of the study, the writer 

 approached the nest with care and stroked the back of the female 

 Vireo several times before she flew from the nest. It is impos- 

 sible, of course, to know to what extent the bird in such a case 

 was possessed of fear of the intruder, and to what extent the fear 

 instinct was subdued by the ascendency of other instincts. For 

 further work along this line there must be devised a method of 

 gauging or standardizing a given instinct or emotion in a ^vild 

 animal. 



So, while birds as fearless as these Vireos seemed to be, can 

 be studied without concealment, it is probably doubtful whether 

 the conclusions as to some forms of action are to be regarded as 

 more than tentative ; and general conclusions can be reached only 

 after numerous repetitions of the studies on the same species.^ 



^Nevertheless I may quote the following extract from my field note-book: "Feed- 

 ing today (July 11) has been very slow, but still I am inclined to think it has been 

 normal. When the birds do come there is practically no evidence of timidity, so 

 that it does not seem likely that they are being restrained at all by fear." 



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