Pairs may remain together all year, joining small flocks with other titmice in winter. Flocks break up in late winter, and pairs establish nesting territories. Male feeds female often from courtship stage until after eggs hatch. Breeding pair may have a "helper," one of their offspring from the previous year. Nest site is in hole in tree, either natural cavity or old woodpecker hole; averages about 35' above the ground, ranging from 3' to 90' up. Unlike the chickadees, apparently does not excavate its own nest hole. Will also use nest boxes. Nest (probably built by female) has foundation of grass, moss, leaves, bark strips, lined with soft materials, especially animal hair. Bird may pluck hair from live woodchuck, dog, or other animal, even from humans. Eggs: 5-6, sometimes 3-9. White, finely dotted with brown, reddish, or purple. Incubation is by female only, 12-14 days. Young: Female stays with young much of time at first, while male brings food; later, young are fed by both parents, sometimes by additional helper. Young leave nest about 15-16 days after hatching.