the Coloration of Eggs. 5G5 



do not seem specially sensitive, and one has sometimes to 

 push the food well down into the throat to get it swallowed, 

 but the markings are probably in part directive nevertheless. 

 The nests are sometimes distinctly dark, and placing one's 

 eye to the opening one often sees only the brilliantly wdiite 

 stars at the corners of the closed mouths. That these are 

 useful to the parents is likely enough from the fact that the 

 young nestlings especially do not necessarily open their 

 mouths on the nests being touched, but do so at once in 

 reaction to a sharp little touch to the bill between the white 

 stars ; and the mouth when opened is yet more clearly 

 indicated by the white flanges. I have seldom myself been 

 able to make out the inner black markings from this 

 position, but it must be different for the bird that has 

 actually entered the nest. In nestlings that I have held in 

 obscurity equivalent (as I judged) to that of the nest, some 

 of the black markings have formed to the eye, a dotted 

 circle surrounding, and to that extent indicating, the gullet ; 

 this may, of course, be their function, though one would 

 have thought the vastly more conspicuous white flanges a 

 quite sufiicient indication. In Spermestes poensis, figured 

 by Bates on p. 590 of * The Ibis' for October 1911, the 

 encircling black-dotted line is replaced by a nearly un- 

 broken lohite circle, which certainly seems as though it 

 must be directive. That this is not the whole explanation, 

 at any rate for Estrilda, is suggested by the fact that some 

 of the spots by no means come into the " directive '' circle, 

 though they certainly contribute to the distinctive appear- 

 ance of the mouth, and that the circle must, in any case, be 

 dim, except to an enemy that has opened the nest ; and by 

 the extraordinary eye-like form taken by the flange- 

 markings in that genus. The opened mouths look like a 

 series of most vicious little demoniac faces, not bird-like at 

 all, with glaring eyes and rows of white teeth. An in- 

 timidating element is quite likely present, but ''hissing" 

 does not correctly describe the extraordinary, rapid, and 

 continuous click-clacking of the young birds. A final point 

 of great possible interest is the fact that the tongue is 



