With birds the far greater part, as has been said, pair and
breed during the spring and early summer, with the exception of the
halcyon.

The halcyon breeds at the season of the winter solstice.
Accordingly, when this season is marked with calm weather, the name of
'halcyon days' is given to the seven days preceding, and to as many
following, the solstice; as Simonides the poet says:

God lulls for fourteen days the winds to sleep

In winter; and this temperate interlude

Men call the Holy Season, when the deep

Cradles the mother Halcyon and her brood.

And these days are calm, when southerly winds prevail at the
solstice, northerly ones having been the accompaniment of the Pleiads.
The halcyon is said to take seven days for building her nest, and
the other seven for laying and hatching her eggs. In our country there
are not always halcyon days about the time of the winter solstice, but
in the Sicilian seas this season of calm is almost periodical. The
bird lays about five eggs.