Page:Bird Haunts and Nature Memories - Thomas Coward (Warne, 1922).pdf/204

150 be noticed. But when the average results are considered the final doom is always the same—all but two of the hopefuls must go to the wall.

A pair of birds may lay an average of four eggs per year for three years; ten out of twelve produced must have negative results; the young if hatched and reared must never become parents, or if more than the two survive in many of the same species we shall at once have a noticeable increase. A small steady increase in the families descended from one pair of birds will, in a few years' time, mean a vast army; any mathematician can demonstrate that. And what does happen when this occurs? for it does constantly in certain species. Simply this, that the joy and success of one species spells sorrow and failure for others. The supply of victuals, whether animal or vegetable, of each species is not inimitable, and when your successful species gets to grips with others the weaker kinds suffer famine. How often do we deplore the decrease, say, of the woodpecker, the chough, the swallow. Do we ever think that there may be any connection between this and the increases we welcome of sterling, jackdaw, swift? That these particular species mentioned have any interdependence is mere theory, and the whole skein is so ravelled that we cannot disentangle its intricate meshes; but there is connection between all increases and decreases. By no means is it certain that the improved breech-loader explains the absence of the great bustard from our open plains, or that the egg~collector wiped out Savi's warbler and threatens the Kentish plover and Dartford warbler; men, in their greed, help to destroy the struggling species, and there is no excuse for this rapacity; but these were struggling when man took a hand in their final extinction. The red-legged partridge, a hungry alien, the go-ahead reed warbler, the ringed plover, and even the willow wren, may have