CHAPTER XII. 



THE FORCE OF HABIT. 



UNDER some conditions habits are formed with surprising quickness. The habit 

 ma}- be of trifling significance and have only a brief reign, but no habits are 

 absolutely rigid, and the genesis of all is probably the same, pleasurable conse- 

 quences following repeated actions which may be forced or accidental. The result is in 

 all cases similar, a mental association of certain things with certain actions. 



While watching hour bv hour the Robins described in Chapter IV, and recording 

 their visits to their young, I began to notice on the third day that the male usually 

 approached on the right side of the nest, that is on the observer's right as he stood facing 

 it, while the female frequently came to the back or on the left. From that time I recorded 

 the manner of each approach, and found that the male invariably came to the right side, 

 and hopped down the limb to his nest. 



In the table given below in which the visits of both birds are recorded for two con- 

 secutive days, R is for the right, L for the left, and B for the far side of the nest with 

 reference to the tent, while the dashes represent visits the character of which was unde- 

 termined. Each sign represents a visit to the nest, at which food was usually served. 



( Female RR RRLBRRRRRBRL - L R - 

 July 27th. Third day of Ob- J - L - - R 



servation 6i hours I Male RBRRRRRRRR RRB RRR- R 



R- 



July 28th. Fourth day of Ob- ( Female I. B B L B B - - B B - 



servation 4 hours. | Male RRRRRRRRRRRRR RRR 



For the fourth day I have no record of the female approaching by the right side, and 

 no record of the male coming in any other way. On the two following days the female 

 did not appear, and as I had reason to believe, was engaged in building a new nest. 

 The male at this period always approached his nest in the habitual manner. Now 

 whether the male bird had formed this habit shortly after the nest was built or shortly 

 after the nesting bough was removed is of little consequence. At all events a definite 

 mode of behavior had developed in a short space of time, in one case in two weeks or in 

 the other in two days. On the fourth day the young had to be brooded often, owing to 

 the heat, which accounts for the apparent inactivity of the female in providing food. 



Probably most birds form definite habits in the manner of approach to the nest, 

 entering on a certain side, or flying to a certain twig, following the path suggested in the 

 first instance by convenience or dictated by caution. A pair of Red-eyed Vireos with 

 whom I spent parts of three days followed a definite course in approach with surprising 



