Like most seabirds, the majority of procellariids breed once a year.

They breed once or twice a year, depending on the species.

They breed once a year and lay two eggs of a similar size.

Most pairs only breed once every three years.

Birds will usually breed once per year, however in good years, with high availability of food, two broods may be produced.

It is likely that each pair which holds a territory attempts to breed once per year.

They only breed once a year, not again in the fall like some species.

Pairs will breed once a year and raise one brood per breeding season.

They breed once a year, in the spring, and give birth about four months later to six to eight young.

Squirrels breed once or twice a year and give birth to a varying number of young after three to six weeks, depending on species.