Rooks are the most conservative birds, and sometimes nothing will
induce them to form a colony where their presence and their cawing
would be the perfecting touches to the trees of some ancestral park.
The most hopeful plan to tempt them is to put up old empty nests or
brooms, or to put rooks' eggs into a nest that happens to be the
desired place for the colony. Their strong preference for certain
sites is curious; they will crowd nest-trees on one side of a road,
and yet pay no attention to other trees of the same sort, seemingly
more perfect for their needs, and only a few yards distant. We have
watched a case where for twenty years the rooks remained faithful to
the original nest-trees of the colony. About ten years ago half these
trees were cut down, and even then the evicted rooks would not build
in trees across the road, though their tops touched the tops of the
favoured trees, which became more crowded with nests than ever. But
two or three seasons ago their favourite nesting-tree, a beech with
far-spread top, began to show signs of disease; and then, after a deal
of wrangling, two or three pairs were permitted to nest in the trees
near by, hitherto despised. In the next season there were nineteen
nests in these trees, and in the next twenty-six. The old beech
meantime grew more and more feeble, as the rooks perhaps discovered
by some brittleness in the twigs at the top; and after one more year,
though it bore foliage, but not so luxuriantly as usual, the tree gave
shelter to only two nests. And now the long-despised trees are the home
of almost the entire colony.
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