White-breasted nuthatch

Appearance

Like other members of its genus, the white-breasted nuthatch has a large head, short tail, short wings, a powerful bill and strong feet; it is 13–14 cm long, with a wingspan of 20–27 cm and a weight of 18–30 g.

The adult male of the nominate subspecies, "S. c. carolinensis", has pale blue-gray upperparts, a glossy black cap, and a black band on the upper back. The wing coverts and flight feathers are very dark gray with paler fringes, and the closed wing is pale gray and black, with a thin white wing bar. The face and the underparts are white. The outer tail feathers are black with broad diagonal white bands across the outer three feathers, a feature readily visible in flight.

The female has, on average, a narrower black back band, slightly duller upperparts and buffer underparts than the male. Her cap may be gray, but many females have black caps and cannot be reliably distinguished from the male in the field. In the northeastern United States, at least 10% of females have black caps, but the proportion rises to 40–80% in the Rocky Mountains, Mexico and the southeastern U.S. Juveniles are similar to the adult, but duller plumaged.

Status

The white-breasted nuthatch is a common species with a large range, estimated at 8,600,000 km2. Its total population is estimated at 10 million individuals, and there is evidence of an overall population increase, so it is not believed to approach either the size criterion or the population decline criterion of the IUCN Red List. For these reasons, the species is evaluated as Least Concern.

Habitat

The breeding habitat of the white-breasted nuthatch is woodland across North America, from southern Canada to northern Florida and southern Mexico. In the eastern part of its range, its preferred habitat is old-growth open deciduous or mixed forest, including orchards, parks, suburban gardens and cemeteries; it is found mainly in the lowlands, although it breeds at 1,675 m altitude in Tennessee. In the west and Mexico, this nuthatch is found in open montane pine-oak woodlands, and nesting occurs at up to 3,200 m altitude in Nevada, California and Mexico. Pinyon-juniper and riverside woodlands may be used locally where available. The white-breasted nuthatch is the only North American nuthatch usually found in deciduous trees; red-breasted, pygmy and brown-headed nuthatches prefer pines.

Reproduction

The white-breasted nuthatch is monogamous, and pairs form following a courtship in which the male bows to the female, spreading his tail and drooping his wings while swaying back and forth; he also feeds her morsels of food. The pair establish a territory of 0.1–0.15 km2 in woodland, and up to 0.2 km2 in semi-wooded habitats, and then remain together year-round until one partner dies or disappears. The nest cavity is usually a natural hole in a decaying tree, sometimes an old woodpecker nest.

The nest hole is usually 3–12 m high in a tree and is lined with fur, fine grass, and shredded bark. The clutch is 5 to 9 eggs which are creamy-white, speckled with reddish brown, and average 19 mm × 14 mm in size. The eggs are incubated by the female for 13 to 14 days prior to hatching, and the altricial chicks fledge in a further 18 to 26 days. Both adults feed the chicks in the nest and for about two weeks after fledging, and the male also feeds the female while she is incubating.

Once independent, juveniles leave the adults' territory and either establish their own territory or become "floaters", unpaired birds without territories. It is probably these floaters which are mainly involved in the irregular dispersals of this species. This species of nuthatch roosts in tree holes or behind loose bark when not breeding and has the unusual habit of removing its feces from the roost site in the morning. It usually roosts alone except in very cold weather, when up to 29 birds have been recorded together.

Food

The white-breasted nuthatch forages along tree trunks and branches in a similar way to woodpeckers and treecreepers, but does not use its tail for additional support, instead progressing in jerky hops using its strong legs and feet. All nuthatches are distinctive when seeking food because they are able to descend tree trunks head-first and can hang upside-down beneath twigs and branches.

This nuthatch is omnivorous, eating insects and seeds. It places large food items such as acorns or hickory nuts in crevices in tree trunks, and then hammers them open with its strong beak; surplus seeds are cached under loose bark or crevices of trees.

The diet in winter may be nearly 70% seeds, but in summer it is mainly insects. The insects consumed by the white-breasted nuthatch include caterpillars, ants, and pest species such as pine weevils, oystershell and other scale insects, and jumping plant lice. This bird will occasionally feed on the ground, and readily visits feeding stations for nuts, suet and sunflower seeds, the last of which it often takes away to store. The white-breasted nuthatch was also observed visiting raccoon latrines in order to find seeds.

The white-breasted nuthatch often travels with small mixed flocks in winter. These flocks are led by titmice and chickadees, with nuthatches and downy woodpeckers as common attendant species. Participants in such flocks are thought to benefit in terms of foraging and predator avoidance. It is likely that the attendant species also access the information carried in the chickadees' calls and reduce their own level of vigilance accordingly.