230 McAtee. Recognition Marks. [aptU 



If liable to considerable individual variation, what dependence 

 can be placed in recognition marks as a means of identifying their 

 fellows, by closely similar species, by Penthestes atricapillus and P. 

 carolincnsis for instance, or Dendroica auduhoni and D. coronata, 

 by the Flickers or Dusky Ducks? One of Wallace's illustrations of 

 recognition marks — those of two species of Scolopax (Darivimsm, 

 fig. 22, p. 225) — certainly does not show more difference than do 

 numerous commonly observed individual variations. One of the 

 fallacies into which coloration theories lead is brought out by a 

 comparison of this figure with that on p. 241 (fig. 23) illustrating 

 a case of mimicry. In the latter cut the objects which are supposed 

 to be so similar that one, the mimic, gains protection b}' the ina- 

 bility of birds to tell the fornas apart, are actually much more 

 different than the two sets of directive markings (shown in the 

 former illustration), which are supposed to be so distinct as to 

 enable the species easily to recognize their kind. 



The variability of recognition marks brings up another question : 

 what must be their extent in order that they may have directive 

 value? Take for example the white tips on the tail feathers of the 

 robin, whi(;h are extremely variable and often absent. In certain 

 warblers we can get a series showing all stages from no tail spots 

 to large blotches on at least two pairs of feathers. Where can the 

 line be drawn? 



Recognition marks are claimed to exist in other groups than 

 birds, even in insects, but in certain cases, becoming more numerous 

 in the lower groups, they are termed warning colors. Where is 

 the line drawn that separates these categories, and why? 



Is there any evidence that birds use in a directive sense the 

 patches of colors, termed recognition marks? 



A valid objection to the theory has been made to the effect that 

 the usefulness or at least the necessity for these marks depends 

 upon the assumption that the animals possessing them are less 

 acute observers than human beings. Humans can readily recog- 

 nize species by glimpses of outline when no color is seen, or by 

 peculiarities of motion, in the case of flight at least, at such dis- 

 tances that the observation of color is entirely out of the question. 

 There is much good evidence furthermore that the assumption 

 mentioned is unfounded. Anyone who has handled live decoy 



