he
vicinity of a preserved trout stream, the more costly neighbour. Indeed
it is the only other bird which nests in colonies of such extent, but
there is this marked difference between herons and rooks, that the
former are sociable only in the colony. When away on its own business,
the heron is among the most solitary of birds, having no doubt, like
many other fishermen, learnt the advantage of its own company.

One of the most remarkable habits in the rook is that of visiting the
old nests in mid-winter. Now and again, it is true, a case of actually
nesting at that season has been noticed, but the fancy for sporting
round the deserted nests is something quite different from this. I have
watched the birds at the nests on short winter days year after year, but
never yet saw any confirmation of the widely accepted view that their
object is the putting in order of their battered homes for the next
season. It seems a likely reason, but in that case the birds would
surely be seen carrying twigs for the purpose, and I never saw them do
so before January. What other attraction the empty nurseries can have
for them is a mystery, unless indeed they are sentimental enough to like
revisiting old scenes and cawing over old memories.

The proximity of a rookery does not affect all people alike. Some who,
ordinarily dwelling in cities, suffer from lack of bird neighbours,
would regard the deliberate destruction of a rookery as an act of
vandalism. A few, as a matter of fact, actually set about establishing
such a colony where none previously existed, an ambition that may
generally be accomplished without extreme difficulty. All that is needed
is to transplant a nest or two of young rooks and lodge them in suitable
trees. The parent birds usually follow, rear the broods, and forthwith
found a settlement for future generations to return to. Even artificial
nests, with suitable supplies of food, have succeeded, and it seems that
the rook is nowhere a very difficult neighbour to attract and establish.

Why are rooks more sociable than ravens, and what do they gain from such
communalism? These are favourite questions with persons informed with an
intelligent passion for acquiring information, and the best answer,
without any thought of irreverence, is "God knows!" It is most certain
that we, at any rate, do not. So far from explaining how it was that
rooks came to build their nests in company, we cannot even guess how the
majority of bi