Birds of the pigeon kind, such as the ringdove and the
turtle-dove, lay two eggs at a time; that is to say, they do so as a
general rule, and they never lay more than three. The pigeon, as has
been said, lays at all seasons; the ring-dove and the turtle-dove
lay in the springtime, and they never lay more than twice in the
same season. The hen-bird lays the second pair of eggs when the
first pair happens to have been destroyed, for many of the hen-pigeons
destroy the first brood. The hen-pigeon, as has been said,
occasionally lays three eggs, but it never rears more than two chicks,
and sometimes rears only one; and the odd one is always a wind-egg.

Very few birds propagate within their first year. All birds,
after once they have begun laying, keep on having eggs, though in
the case of some birds it is difficult to detect the fact from the
minute size of the creature.