The white-breasted nuthatch (Sitta carolinensis) is a small songbird of the nuthatch family
which breeds in old-growth woodland across much of temperate North
America. It is a stocky bird, with a large head, short tail, powerful
bill, and strong feet. The upperparts are pale blue-gray, and the face
and underparts are white. It has a black cap and a chestnut lower belly.
The nine subspecies differ mainly in the color of the body plumage.
Like other nuthatches,
the white-breasted nuthatch forages for insects on trunks and branches
and is able to move head-first down trees. Seeds form a substantial part
of its winter diet, as
do acorns and hickory nuts that were stored by the bird in the fall. The nest is in a hole in a tree, and the breeding pair may smear insects around the entrance as a deterrent to squirrels. Adults and young may be killed by hawks, owls, and snakes, and forest clearance may lead to local habitat loss, but this is a common species with no major conservation concerns over most of its range.
do acorns and hickory nuts that were stored by the bird in the fall. The nest is in a hole in a tree, and the breeding pair may smear insects around the entrance as a deterrent to squirrels. Adults and young may be killed by hawks, owls, and snakes, and forest clearance may lead to local habitat loss, but this is a common species with no major conservation concerns over most of its range.
Taxonomy
The nuthatches are a genus, Sitta, of small passerine birds which
derive their English name from the propensity of some species to wedge
large insects or seeds into cracks, and then hack at them with their
strong bills.[4] Sitta is derived from sittē, the Ancient Greek for nuthatch,[5] and carolinensis means "of Carolina" in Latin. The white-breasted nuthatch was first described by English ornithologist John Latham in his 1790 work, the Index Ornithologicus.[6]
Nuthatch taxonomy is complex, with geographically separated species
sometimes closely resembling each other. The white-breasted nuthatch has
an appearance and contact call similar to those of the white-cheeked nuthatch, Sitta leucopsis, of the Himalayas and was formerly considered to be conspecific with it.[2] A
study published in 2012 showed that four distinct lineages were
genetically isolated from each other and could represent different
species, recognizable by morphology and song.[7] A
molecular phylogeny published in 2014 and including all main species'
lineages within nuthatches concluded that the white-breasted nuthatch
was more closely related to the giant nuthatch (S. magna) than to S. przewalskii, formerly regarded as possibly conspecific with it; S. przewalskii turned out to be basal in the family.[8]
Description
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 (5.1–5.5 in) long, with a wingspan of 20–27 cm (7.9–10.6 in)
and a weight of 18–30 g (0.63–1.06 oz).[3]
The adult male of the nominate subspecies, S. c. carolinensis, has pale blue-gray upperparts, a glossy black cap (crown of the head), 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.[2]
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.[2]
Like other nuthatches, this is a noisy species with a range of vocalizations. The male's mating song is a rapid nasal qui-qui-qui-qui-qui-qui-qui. The contact call between members of a pair, given most frequently in the fall and winter is a thin squeaky nit, uttered up to 30 times a minute. A more distinctive sound is a shrill kri repeated rapidly with mounting anxiety or excitement kri-kri-kri-kri-kri-kri-kri-kri; the Rocky Mountains and Great Basin subspecies have a higher, faster yididitititit call,[2] and Pacific birds a more nasal beeerf.[9]
Three other, significantly smaller, nuthatches have ranges which overlap
that of white-breasted, but none has white plumage completely
surrounding the eye. Further distinctions are that the red-breasted nuthatch has a black eye line and reddish underparts, and the brown-headed and pygmy nuthatches each have a brown cap, and a white patch on the nape of the neck.[9]
Geographical variation
The white-breasted nuthatch has nine subspecies, although the
differences are small and change gradually across the range. The
subspecies are sometimes treated as three groups based on close
similarities in morphology,
habitat usage, and vocalizations. These groups cover eastern North
America, the Great Basin and central Mexico, and the Pacific coastal
regions.[9] The subspecies of the western interior have the darkest upperparts, and eastern S. c. carolinensis has the palest back.[2] The
eastern form also has a thicker bill and broader dark cap stripe than
the interior and Pacific races. The calls of the three groups differ, as
described above.[9] The Great Basin and Eastern forms have been observed in secondary contact on the Great Plains, where they do not seem to mix.
| Subspecies[2] | Range | Appearance |
|---|---|---|
| S. c. carolinensis | Nominate subspecies, northeast North America west to Saskatchewan and eastern Texas | Palest back and cap |
| S. c. nelsoni | Rocky Mountains, from northern Montana south to extreme northwest Chihuahua | Darker gray upperparts, darker cap, less contrast in wings |
| S. c. tenuissima | From British Columbia through the Cascade Range to southern California | Smaller than S. c. nelsoni, with slightly paler upperparts and a more slender bill |
| S. c. aculeata | Western parts of Washington, Oregon and California, northernmost Baja California. | Smaller than S. c. tenuissima, with buffer underparts, slightly paler upperparts and a more slender bill |
| S. c. alexandrae | Northern Baja California | Larger than S. c. aculeata, with marginally darker upperparts. The longest-billed race |
| S. c. lagunae | Southernmost Baja California | Smaller than S. c. alexandrae with slightly darker; underparts and more buff. Bill relatively stout |
| S. c. oberholseri | Southwest Texas and eastern Mexico | Very similar to S. c. nelsoni, but upperparts and underparts slightly darker |
| S. c. mexicana | Western Mexico | Duller than S. c. oberholseri with grayer flanks |
| S. c. kinneari | Southern Mexico in Guerrero and Oaxaca | Smallest subspecies, similar to S. c. mexicana but female has more extensively orange-buff underparts. Short, stout bill |
Distribution and 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 (5,495 ft) 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 (10,500 ft) altitude in Nevada, California and Mexico.[2] Pinyon-juniper and riverside woodlands may be used locally where available.[10] The
white-breasted nuthatch is the only North American nuthatch usually
found in deciduous trees; red-breasted, pygmy and brown-headed
nuthatches prefer pines.[9]
The presence of mature or decaying trees with holes suitable for nesting is essential, and trees such as oak, beech and hickory are favored in the east since they provide edible seeds.[2] Although suitable habitat is distributed continentally, it is discontinuous, and the separate populations of this non-migratory species have diverged to form distinct regional subspecies.[11]
This nuthatch, like most of its genus, is non-migratory, and the adults
normally stay in their territory year-round. There may be more
noticeable dispersal due to seed failure or high reproductive success in
some years,[12] and this species has occurred as a vagrant to Vancouver Island, Santa Cruz Island, and Bermuda. One bird landed on the RMS Queen Mary six hours sailing east of New York City in October 1963.[2]
Behavior
Breeding
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.[12] The pair establish a territory of 0.1–0.15 km2(25–37 acres) in woodland, and up to 0.2 km2 (49 acres) in semi-wooded habitats, and then remain together year-round until one partner dies or disappears.[13] The nest cavity is usually a natural hole in a decaying tree, sometimes an old woodpecker nest.[2]
The nest hole is usually 3–12 m (9.8–39.4 ft) 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 (0.75 in × 0.55 in) 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.[3] 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.[2]
Predation
Predators of adult nuthatches include owls and diurnal birds of prey (such as sharp-shinned and Cooper's hawks), and nestlings and eggs are eaten by woodpeckers, small squirrels, and climbing snakes such as the western rat snake. The white-breasted nuthatch responds to predators near the nest by flicking its wings while making hn-hn calls.
When a bird leaves the nest hole, it wipes around the entrance with a
piece of fur or vegetation; this makes it more difficult for a predator
to find the nest using its sense of smell.[13] The nuthatch may also smear blister beetles around the entrance to its nest, and it has been suggested that the unpleasant smell from the crushed insects deters squirrels, its chief competitor for natural tree cavities.[14] The estimated average lifespan of this nuthatch is two years,[13] but the record is twelve years and nine months.[12]
This nuthatch's responses to predators may be linked to a reproductive
strategy. A study compared the white-breasted nuthatch with the
red-breasted nuthatch in terms of the willingness of males to feed
incubating females on the nest when presented with models of predators.
The models were of a sharp-shinned hawk, which hunts adult nuthatches,
and a house wren, which destroys eggs.[15] The
white-breasted nuthatch is shorter-lived than the red-breasted
nuthatch, but has more young, and was found to respond more strongly to
the egg predator, whereas the red-breasted showed greater concern with
the hawk. This supports the theory that longer-lived species benefit
from adult survival and future breeding opportunities, while birds with
shorter life spans place more value on the survival of their larger
broods.
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