There is another point which should not be overlooked. It has after all become a mere fiction to say that all places are occupied. Nature's nice order has been destroyed, and her kingdom thrown into the utmost confusion; our action tends to maintain the disorderly condition, while she is perpetually working against us to re-establish order. When she multiplies some common, little-regarded species to occupy a space left vacant by an artificially exterminated kind, the species called in as a mere stop-gap, as it were, is one not specially adapted in structure and instincts to a particular mode of life, and consequently cannot fully and effectually occupy the
HERON.
. . . the streams are fished by herons.'
EXOTIC BIRDS FOR BRITAIN 175
ground into which it has been permitted to enter. To speak in metaphor, it enters merely as a caretaker or ignorant and improvident steward in the absence of the rightful owner. Again, some of our ornamental species, which are fast diminishing, are fitted from their peculiar structure and life habits to occupy places in nature which no other kinds, however plastic they may be, can even partially fill. The wryneck and the woodpecker may be mentioned; and a still better instance is afforded by the small, gem-like kingfisher
--the only British bird which can properly be described as gem-like. When the goldfinch goes