This activity, which is carried on throughout the nesting period, is thought to deter insects, small mammals, and other birds from entering the nest cavity. Several observers have noted that Red-breasted Nuthatches have a habit of flying straight into the entrance hole, without alighting on the outside of the cavity first, perhaps to avoid the pitch smeared around the hole. Egg Laying Clutch sizes range from four to seven eggs, with five or six being the usual number. Incubation is probably done by the female alone. Both adults tend the nestlings.
Discrepancies exist as to the length of time the nestlings spend in the nest.
A general range is 18 to 21 days, but one source reports 14 days. The number of broods produced in one breeding season and whether this species produces replacement broods are unknown. Unlike other Nuthatches, Red-breasted Nuthatches do not always remain on their territories year round. They may move southward in the fall, or they may remain in the north throughout the winter, depending on the state of the cone crop. They have expanded their breeding range into some eastern states by using ornamental conifers for nesting.