l departure from the normal routine
comes as something of a surprise; for the days are still short, the
temperature is still low, the nesting season is still many weeks ahead,
and yet for part of the day, and for just that part when the promptings
of hunger must be strongest, the male, instead of joining the flock,
isolates itself and expends a good deal of energy in insuring that its
isolation shall be complete. And in place of the silence we hear from
all directions the cheerful song uttered with such marked persistency
that it almost seems as if the bird itself must be aware that by doing
so it was advertising the fact of its occupation of a territory. This is
surely a remarkable change, and the females in the meantime continue
their winter routine.

One other example. The monotonous call of the Greenfinch is probably
familiar to all. In winter these birds accompany other Finches and form
with them flocks of varying sizes, but in the spring the flocks
disperse, and the Greenfinch, in common with other units of the flock,
alters its mode of life. But whereas the Chaffinch or the Bunting begins
to acquire its territory in February, the Greenfinch only does so in
April. When the organic changes do at length begin to make themselves
felt, the male seeks a position of its own, and having found one remains
there, uttering its characteristic call. But owing probably to the fact
that it is much later than the aforementioned species in acquiring a
territory, temporary desertions are not so much in evidence. The species
is so very plentiful, and the bird is so prone to nest in gardens and
shrubberies surrounding human habitations, that this seasonal change in
its routine of existence cannot fail to be noticed. One can hear its
call in every direction, one can watch the same individual in the same
tree; and it is the male that is thus seen and heard, the female appears
later. Thus the behaviour falls into line with that of the Bunting or
the Chaffinch.

The behaviour of these resident species throws some light upon the early
arrival of the males which we are endeavouring to explain in the case of
the migrants. Let us see how their actions compare. The male resident
deserts the female early in the year and establishes itself in a
definite position, where it advertises its presence by song; the male
migrant travels from a great distance, arrives later, and also
establishes itself in a definite position, where it, too, advertises