APPENDIX E 493 



cape observation, and its coloration and squatting attitude enabling it 

 thus to escape observation; as Mr. Beddard puts it in his book on "Ani- 

 mal Coloration," "absence of movement is absolutely essential for pro- 

 tectively colored animals, whether they make use of their coloration for 

 defensive purposes or offensive purposes." So far as Mr. Thayer's book 

 or similar books confine themselves to pointing out cases of this kind, and 

 to working on hypotheses where the facts are supplied by such cases, they 

 do a real service. But it is wholly different when the theory is pushed 

 to fantastic extremes, as by those who seek to make the coloration of 

 big game animals such as zebras, giraffes, hartebeests and the like, pro- 

 tective. I very gravely doubt whether some of the smaller mammals 

 and birds to which Mr. Thayer refers really bear out his theory at all. 

 He has, for instance, a picture of blue jays by snow and blue shadow, 

 which is designed to show how closely the blue jay agrees with its sur- 

 roundings (I would be uncertain from the picture whether it is really blue 

 water or a blue shadow). Now it is a simple physical impossibility that 

 the brilliant and striking coloration of the blue jay can be protective 

 both in the bare woods when snow is on the ground and in the thick 

 leafy woods of midsummer. Countless such instances could be given. 

 Mr. Thayer insists, as vital to his theory, that partridges and other pro- 

 tectively colored animals owe their safety, not at all to being incon- 

 spicuously colored, that is, to being colored like their surroundings, but 

 to their counter-shading, to their being colored dark above and light 

 below. But as a matter of fact most small mammals and birds which 

 normally owe their safety to the fact that their coloration matches their 

 surroundings, crouch flat whenever they seek to escape observation; 

 and when thus crouched flat, the counter-shading on which Mr. Thayer 

 lays such stress almost, or completely, disappears. The counter-shading 

 ceases to be of any use in concealing or protecting the animal at the precise 

 moment when it trusts to its coloration for concealment. Small rodents 

 and small dull-colored ground birds are normally in fear of foes which 

 must see them from above at the critical moment if they see them at all; 

 and from above no such shading is visible. This is true of almost all the 

 small birds in question, and of the little mice and rats and shrews, and 

 it completely upsets Mr. Thayer's theory as regards an immense pro- 

 portion of the animals to which he applies it; most species of mice, for 

 example, which he insists owe their safety to counter-shading, live under 

 conditions which make this counter-shading of practically no consequence 



