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 be seen on these open, sandy tracts, the abode of the peewit, stone-curlew, ringed plover, red-legged partridge, and other such waste-haunting species. But the nesting habits of a bird must follow its general ones almost necessarily in the first instance, and though there are many apparently striking instances to the contrary, they are probably to be explained by the former having remained fixed whilst the latter have changed. No doubt, therefore, the stock-dove began to spend much of its time on the ground before it thought of laying its eggs there, and of the facilities offered by rabbit-holes for so doing. That the habits as well as the organisms of all living creatures are in a more or less plastic and fluctuating state is, I believe, a conclusion come to by Darwin, and it agrees entirely with the little I have been able to observe in regard to birds. I have seen the robin redbreast become a wagtail or stilt-walker, the starling a wood-pecker or fly-catcher, the tree-creeper also a fly-catcher, the wren an accomplished tree-creeper, the moor-hen a partridge or plover, and so on, and so on, all such instances having been noted down by me at the time. Most birds are ready to vary their habits suddenly and de novo if they can get a little profit on the transaction, and the extent to which they have varied gradually in a long course of time and under changed conditions is, of course, a commonplace after Darwin. The wood-pigeon has not yet begun to lay its eggs in rabbit-holes or anywhere but in trees and bushes, but that it may some day do so is not improbable, for it comes down sometimes, though not very frequently, on the same sandy wastes that are loved by the stock-dove,