direction. Thus gulls, terns, and many other sea birds, which fly between 

 blank ocean and blank sky, getting their food from the water, are largely 

 cloaked in sky-matching white. So, among land birds, are the often-men- 

 tioned Snowy Owl and White Gerfalcon, which fly and hunt over treeless 

 barrens and the bare ocean-shore. So are most swans, some geese, some pel- 

 icans, and several herons, storks, ibises, cranes, etc., — birds that swim or 

 wade, seeking their food below them in the water, and doubtless subject, in 

 all or most cases, to persecutions from aquatic enemies. Showy as these 

 birds are against the muddy ground and dark-green vegetation, they are 

 equipped for the utmost possible inconspicuousness when seen from below, 

 against the sky. Viewed at the proper angle, they must, like the skunk's 

 back, be almost invisible, especially at night. (An opaque body directly in- 

 terposed between the beholder and the zenith cannot fail to show dark, however 

 colored; but the upper surfaces of a snow-white opaque body looked at in an 

 obliquely upward direction, so that it is seen sky-lit and at the same time 

 against the sky, may exactly match the brightness of its luminous background 

 —all of which is shown by Figs. 107-115.) Plates VIII, IX, and X, 

 with their Flamingoes and Roseate Spoonbills, reveal the simple fact, which 

 seems never to have been noticed, that these traditionally " showy" birds 

 are, at their most critical moments, perfectly 'obliterated' by their colora- 

 tion. Conspicuous, in most cases, when looked at from above, as man is apt 

 to see them, they are wonderfully fitted for 1 vanishment' against the flushed, 

 rich-colored skies of early morning and evening; and such are their normal 

 backgrounds, at their chief feeding-times, in relation to their aquatic enemies 

 (sharks, alligators, tortoises, anacondas, etc.) and those of their prey that 

 see at all. Of course, against the dawn or the sunset itself, these birds must 

 show dark, just as with white against the zenith; but the rosy hues very com- 

 monly suffuse both sides of the sky, so that, in either twilight, the Spoonbill's, 

 Ibis's or Flamingo's illuminated ruddy color very often has a true 'back- 

 ground' of illuminated ruddy sky. Further, the side of such a bird actually 

 sunlit, at early morning or late afternoon, is made to glow so brilliantly as to 



154 



