32 Palmer, Instinctive Stillness in Birds. [jan 



heron and remaining still I have found that I could sometimes 

 touch the fish and even have them nibble at my finger or toe, while 

 an unexpected and sudden motion on my part would cause them to 

 rapidly vanish. The cautious movement of the heron inviting 

 confidence is the more readily productive of good results, while it 

 is doubtful if the escaping fish in any degree realize that one of 

 their companions has disappeared. They merely escaped a sudden 

 motion of something larger than themselves, their own memory 

 and knowledge being of the smallest. 



Dark-bodied, day-feeding herons obtain their food almost entirely 

 where the fringe of vegetation, sedges, bushes, or more distant tree 

 tops, make a background and prevent the shape of the birds from 

 affecting the skyline as seen by the prey. This is to a much less 

 extent the case with the light-bodied and light -fronted species which 

 are apt to feed largely at a distance from trees and bushes. In this 

 latter phase of aggressive mimicry, whether the prospective victim 

 is fish, reptile, or batrachian, stillness and caution are quite essential 

 and the value of protective and simulative coloring is the same, for 

 light colored birds, when motionless, harmonize with the colors of 

 the sky as seen from the position of the prey. The sharp eyes of 

 the heron search every likely spot; its absence of motion invites 

 confidence, possibly some inclination to move; it has time to ex- 

 amine well, while its colors and markings, as viewed from in front 

 and below, blend perfectly, or at least sufficiently, with its usual 

 background, and an adequate amount of food is secured. The 

 balance of trade is always in favor of the aggressor if his stock of 

 patience is sufficient. The light patches and streaks on the neck 

 front of some herons may be explained as a phase of aggressive 

 mimicry. They serve to break up the contours and colors of the 

 bird and suggest, instinctively, openings and irregularities in the 

 background of vegetation. 



Color mimicry would seem to be a station, somewhat different in 

 different species, at which the color development was largely left 

 at a very early period of its life's history. Assuming that the 

 archaic ancestral bird was of a uniform tint with unspecialized 

 feathers it would seem that as the specialization of the feathering 

 developed so the color gradation tints necessarily came into effect, 

 not for mimicry, however, but as a physiological result, the functions, 



