218 The Naturalist in Li Plata.
from all competition with other birds as the solitary savage is removed from the struggle of life affecting and modifying men in crowded communities. The lower kind of competition affecting hummingbirds, that with insects and, within the family, of species with species, has probably only served to intensify their unique characteristics, and, perhaps, to lower their intelligence.
Not only are they removed from that indirect struggle for existence which acts so powerfully on other families, but they are also, by their habits and the unequalled velocity of their flight, placed out of reach of that direct war waged on all other small birds by the rapacious kinds--birds, mammals, and reptiles. One result of this immunity is that humming-birds are excessively numerous, albeit such slow breeders; for, as we have seen, they only lay two eggs, and not only so, but the second egg is often dropped so long after incubation has begun in the first that only one is really hatched. Yet Belt expressed the opinion that in Nicaragua, where he observed humming-birds, they out-numbered all the other birds together. Considering how abundant birds of all kinds are in that district, and that most of them have a protective colouring and lay several eggs, it would be impossible to accept such a statement unless we believed that humming-birds have, practically, no enemies.
Another result of their immunity from persecution is the splendid colouring and strange and beautiful feather ornaments distinguishing them above all other birds; and excessive variation in this direction is due, it seems to me, to the very
Humming-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 intense, yet seemingly so evanescent!--the glittering 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.
Excessive 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 existence 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 brilliant plumage; but the rapacious kinds do not waste their energies in the vain pursuit of hummingbirds. These are in the position of neutrals, free to range at will amidst the combatants, insulting
220 The Naturalist in La Plata.