Flumming- Birds. 219 
causes which serve to check variation in all other 
directions. In their plumage, as Martin long ago 
wrote, nature has strained at every variety of effect 
and revelled in an infinitude of modifications. How 
wonderful their garb is, with colours so varied, so 
inteuse, yet seemingly so evanescent !—the glitter- 
ing mantle of powdered gold; the emerald green 
that changes to velvet black; ruby reds and 
luminous scarlets ; dull bronze that brightens and 
burns like polished brass, and pale neutral tints 
that kindle to rose and lilac-coloured flame. And 
to the glory of prismatic colouring are added feather 
decorations, such as the racket-plumes and downy 
muffs of Spathura, the crest and frills of Lophornis, 
the sapphire gorget burning on the snow-white 
breast of Oreotrochilus, the fiery tail of Cometes, 
and, amongst grotesque forms, the long pointed 
crest-feathers, representing horns, and flowing 
white beard adorning the piebald goat-like face of 
Oxypogon. 
Hxcessive variation in this direction is checked 
in nearly all other birds by the need of a protective 
colouring, few kinds so greatly excelling in strength 
and activity as to be able to maintain their exis- 
tence without it. Bright feathers constitute a 
double danger, for not only do they render their 
possessor conspicuous, but, just as the butterfly 
chooses the gayest flower, so do hawks deliberately 
single out from many obscure birds the one with 
brilhant plumage; but the rapacious kinds do not 
waste their energies in the vain pursuit of humming- 
birds. These are in the position of neutrals, free 
to range at will amidst the combatants, insulting 
