for leaving. The winter had been one of continued drought; the dry grass
and herbage of the preceding year had been consumed by the cattle and
wild animals, or had turned to dust, and with the disappearance of their
food and cover the mice had ceased to be. The famine-stricken cats
sneaked back to the house. It was pitiful to see the little burrowing
owls; for these birds, not having the powerful wings and prescient
instincts of the vagrant Otus brachyotus, are compelled to face the
poverty from which the others escape. Just as abundance had before made
the domestic cats wild, scarcity now made the burrowing owls tame and
fearless of man. They were so reduced as scarcely to be able to fly, and
hung about the houses all day long on the look-out for some stray morsel
of food. I have frequently seen one alight and advance within two or
three yards of the door-step, probably attracted by the smell of roasted
meat. The weather continued dry until late in spring, so reducing the
sheep and cattle that incredible numbers perished during a month of cold
and rainy weather that followed the drought.

How clearly we can see in all this that the tendency to multiply
rapidly, so advantageous in normal seasons, becomes almost fatal to a
species in seasons of exceptional abundance. Cover and food without
limit enabled the mice to increase at such an amazing rate that the
lesser checks interposed by predatory species were for a while
inappreciable. But as the mice increased, so did their enemies.
Insectivorous and other species acquired the habits of owls and weasels,
preying exclusively on them; while to this innumerable army of residents
was shortly added multitudes of wandering birds coming from distant
regions. No sooner had the herbage perished, depriving the little
victims of cover and food, than the effects of the war became apparent.
In autumn the earth so teemed with them that one could scarcely walk
anywhere without treading on mice; while out of every hollow weed-stalk