Breeding season: April–June, one brood per season (sometimes two in southern Sweden). - Nest: in tree holes, nest boxes (hole 28 mm) and wall cracks. Mosses, lichens and hair. - Eggs: 8–12, white with red spots. Incubated for 13–14 days by the female. - Young: both parents feed them with insects and larvae. They fledge after 18–21 days.