258 



Bird - Lore 



gives superiority in briglitness of color- 

 ation, in ornamentation, and in bodily 

 vigor, to the male) has been so strong as 

 completely to overcome all tendencies 

 that make for a dull or concealing color- 

 ation in the male. The white so common 

 on the outer tail feathers of birds, which is 

 only shown in flight, must represent a totally 

 dififerent tendenc}^ or set of tendencies; 

 it is advertising; it is sometimes displayed 

 in courtship; it may serve as a recognition 

 mark, when the birds are in a flock; by its 

 display in flight and its disappearance the 

 instant a bird alights, it may mislead a 

 pursuer; and of any pair of closelj' aUied 

 species, such as the Vesper Finch and 

 Savanna Sparrow, or Mocking Bird and 

 Catbird, one maj' possess it and the other 

 lack it, without any apparent difference 

 in habits being produced thereby; while 

 even in the same species, as in the Robin, 

 one form may possess these white mark- 

 ings, while another form lacks them. 



"(8) There are only rarely cases in 

 which under the same conditions, all 

 the kinds of concealing coloration tend 

 to be of the same type. This is another 

 way of saying, both that the principle o"" 

 natural selection working toward a con- 

 cealing coloration is in every case com- 

 plicated by the workings of other princi- 

 ples and tendencies, and also that even 

 birds and mammals of comparatively re- 

 stricted life-areas live under conditions of 

 sufficient variety to make it impossible to 

 develop coloration patterns showing such 

 complete mimicry of their surroundings as 

 are shown by the coloration patterns of 

 certain insects and even reptiles. Under 

 most conditions of bird and mammal life, 

 one pattern seems about as good as an- 

 other if of the right general tint. Obser- 

 vers who get obsessed by their theory often 

 pick out with triumph peculiarities which 

 have no effect whatever, or even the re- 

 verse effect of that which they ascribe to 

 them, and speak as if these peculiarities 

 were essential to concealment. Thus it 

 is alleged that the black tip of the ermine's 

 tail, and the black tails of certain species 

 of Ptarmigan, are concealing; yet the 

 Arctic fox has no black tip to its tail, and 



there are white-tailed Ptarmigan. It is 

 evident that either the black on the tails 

 of the weasel and of some Ptarmigan has 

 no especial effect, or else that the lack of 

 it on the tails of the fox and of other 

 Ptarmigan, does have a special effect. 

 If the black tail is concealing, then the 

 white tail is revealing; and vice versa; or 

 else no particular effect is produced either 

 way. Doubtless the last is the case. Not 

 only are minute patterns rarely of any 

 real weight in concealing their wearers, 

 but wide differences of pattern have no 

 effect, if the general hue is one in sufficient 

 harmony with the ordinary surroundings. 

 This becomes apparent when we consider 

 the utterh' different coloration patterns 

 of different Sparrows, Warblers, and 

 Thrushes which live under substantially 

 the same conditions and are equally hard 

 to make out. A careful examination of 

 those birds which reallj' do have a con- 

 cealing coloration, and may be beneficially 

 affected thereby, goes to show that with 

 the possible exception of a very few cases, 

 it is out of the question that all the widely 

 varying types of coloration, in any given 

 set of surroundings, can have been pro- 

 duced by the same agency. In so far as 

 the principle of natural selection, working 

 toward the production of a concealing 

 coloration, has affected all these numerous 

 species of birds, it has done so, not by pro- 

 ducing each of the countless and totally 

 different types of coloration, but by set- 

 ting bounds beyond which the coloration 

 cannot vary in any advertising direction, 

 and allowing other circumstances to de- 

 termine the exact pattern within these 

 bounds. As already shown, countershad- 

 ing, among birds and mammals, gener- 

 ally plays an insignificant or negligible 

 part in helping produce a concealing 

 coloration. 



"(9) In many situations, the quality of 

 the landscape, or the quality of the cover, 

 is such that neither any concealing quality 

 in the coloration, nor any advertising 

 quality, is of more than infinitesimal con- 

 sequence to the animal compared with the 

 development of other qualities — wariness, 

 shrewdness, courage, speed, insistence 



