| White-breasted nuthatch | |
|---|---|
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| Adult maleS. c. carolinensis inGreen-Wood Cemetery, New York, USA | |
| Song of an individual fromWilkes County, North Carolina | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Sittidae |
| Genus: | Sitta |
| Species: | S. carolinensis |
| Binomial name | |
| Sitta carolinensis Latham, 1790 | |
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| Approximate distribution map Year-round Nonbreeding | |
Thewhite-breasted nuthatch (Sitta carolinensis) is aspecies of bird in the nuthatch familySittidae. It is a medium-sized nuthatch, measuring approximately 15.5 cm (6.1 in) in length. Coloration varies somewhat along the species' range, but theupperparts are light blue-gray, with a blackcrown and nape in males, while females have a dark gray crown. Theunderparts are whitish, with a reddish tinge on the lower abdomen. Despite not being closely related, the white-breasted nuthatch and thewhite wagtail are very similar in plumage.[2]
The white-breasted nuthatch is a chatty bird. It has a nasal voice and often utters little cries or vocalizations, often composed of repetitions of small invariant whistles. In summer, it is an exclusivelyinsectivorous bird, consuming a wide range ofarthropods, but in winter its diet consists mainly ofseeds. The nest is located in the cavity of a tree. Theclutch consists of five to nine eggs, incubated for two weeks by the female, who is fed by the male. The two adults then feed the young until theyfledge, and for a few weeks after that.[3]
The white-breasted nuthatch breeds throughout much ofNorth America,[4] except in the cooler and drier areas. It is mainly found at low elevations, indeciduous forests or in mixedwoodlands.[4] Seven to nine subspecies are generally distinguished by their slightly distinct distributions, vocalizations, and coloration. The species was once thought to be related to thewhite-cheeked nuthatch (S leucopsis) andPrzewalski's nuthatch (S. przewalskii), two species fromsouthern Asia, but is actually more closely related to thegiant nuthatch (S. magna), also fromSoutheast Asia.
Thenuthatches are agenus,Sitta, of smallpasserinebirds which derive their English name from the tendency of some species to wedge large insects or seeds into cracks, and then hack at them with their strong bills.[5]Sitta is derived fromsittē,Ancient Greek for nuthatch,[6] andcarolinensis means "of Carolina" inLatin. The white-breasted nuthatch was first described by English ornithologistJohn Latham in his 1790 work, theIndex Ornithologicus.[7] German ornithologistHans Edmund Wolters proposed the division of the genusSitta into subgenera in 1975–1982. The white-breasted nuthatch is placed inSitta (Leptositta)(Buturlin, 1916), alongside thewhite-cheeked nuthatch (S. leucopsis) andPrzewalski's nuthatch (S. przewalskii).[8]
Nuthatch taxonomy is complex, with geographically separated species sometimes closely resembling each other. In appearance, the white-breasted nuthatch is similar to the white-cheeked nuthatch of theHimalayas, and was historically sometimes even considered to beconspecific with it.[9][10] 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.[11] Molecularphylogenies published in 2014 and 2020 and including all main species' lineages within nuthatches concluded that the white-breasted nuthatch was more closely related to thegiant nuthatch (S. magna) than to either white-cheeked or Przewalski's nuthatches; these latter two turned out to bebasal in the family.[12][13]
The simplifiedcladogram below is based on thephylogenetic analysis by Päckert and colleagues (2020):[13]
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The white-breasted nuthatch is a medium-sized nuthatch, measuring about 15.5 cm (6.1 in) in length.[14] Like other members of its genus, it 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).[15]
The adult male of thenominate subspecies,S. c. carolinensis, has pale blue-grayupperparts, a glossy black cap (crown of the head), and a black band on the upper back. Thewing coverts andflight 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 theunderparts are white. The outer tail feathers are black with broad diagonal white bands across the outer three feathers, a feature readily visible in flight.[14]
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 northeasternUnited States, at least 10% of females have black caps, but the proportion rises to 40–80% in theRocky Mountains,Mexico and the southeastern U.S. Juveniles are similar to the adult, but duller plumaged.[14]
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 thered-breasted nuthatch has a black eye line and reddish underparts, and thebrown-headed andpygmy nuthatches each have a brown cap, and a white patch on the nape of the neck.[16]
The white-breasted nuthatch currently has seven accepted subspecies,[17] although the differences are small and change gradually across the range. The subspecies are treated in two to four groups based on close similarities inmorphology, habitat usage, and vocalizations.[18] These groups cover eastern North America, theGreat Basin and central Mexico, and the Pacific coastal regions.[16] A proposal was made to theAmerican Ornithologists Union in 2013 to split these groups into two, three, or four separate species;[19] this was not passed due to insufficient evidence, but with an expectation to revisit the status when further evidence becomes available.[20][21] The subspecies of the western interior have the darkest upperparts but a narrower dark crown above the white cheeks, and easternS. c. carolinensis has the palest back, but a broader dark crown above the cheeks.[14][21] The eastern form also has a thicker bill than the interior and Pacific races.[21] The calls of the three groups differ, as described above.[16] The exact boundaries of the subspecies within California was examined in a 2017 paper, revising the previously believed boundaries.[22]
| Subspecies[17][22] | Image | Range | Appearance |
|---|---|---|---|
| S. c. carolinensis |  Algonquin Provincial Park, Ontario | Nominate subspecies, northeast North America west toSaskatchewan and easternTexas | Palest back and cap |
| S. c. nelsoni | .jpg) Edmonton, Alberta | Rocky Mountains, from southernAlberta south to northwestChihuahua, southwest Texas and eastern Mexico | Darker gray upperparts, darker cap, less contrast in wings; includesS. c. oberholseri |
| S. c. tenuissima |  Fort Rock, central Oregon | FromBritish Columbia through theCascade Range to southernCalifornia in the Sierra Nevada at higher altitudes | Smaller thanS. c. nelsoni, with slightly paler upperparts and a more slender bill |
| S. c. aculeata | 5.jpg) Groveland, Central Valley, California | Western parts ofWashington,Oregon and California, west of the Cascades and Sierra Nevada, at lower altitudes | Smaller thanS. c. tenuissima, with buffer underparts, slightly paler upperparts and a more slender bill |
| S. c. alexandrae |  Sierra de San Pedro Mártir, Baja California | Northern Baja California | Larger thanS. c. aculeata, with marginally darker upperparts; the longest-billed race |
| S. c. lagunae |  Sierra La Laguna, Baja California Sur | Southernmost Baja California Sur | Smaller thanS. c. alexandrae with slightly darker; underparts and more buff; bill relatively stout |
| S. c. mexicana |  Namiquipa, Chihuahua | Western and southern Mexico | Duller thanS. c. nelsoni with grayer flanks; short, stout bill; includesS. c. kinneari |
Only three other species of nuthatches inhabit North America, the red-breasted nuthatch (S. canadensis), the pygmy nuthatch (S. pygmaea) and the brown-headed nuthatch (S. pusilla); their distributions all overlap with those of the white-breasted nuthatch. They are, however, clearly distinct and much smaller, since they are the smallest nuthatches, measuring 10 centimeters long and weighing around 10 grams.[23] The red-breasted nuthatch has reddish underparts and has a black stripe on the eye. The pygmy nuthatch and the brown-headed nuthatch have a brown crown with a white spot on the nape.[16]
The breeding habitat of the white-breasted nuthatch is woodland acrossNorth America, from southern Canada to northern Florida and southern Mexico. In the eastern part of its range, its preferred habitat is old-growth opendeciduous 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) elevation inTennessee. In the west and Mexico, the white-breasted nuthatch is found in openmontanepine-oak woodlands, and nesting occurs at up to 3,200 m (10,500 ft) elevation in Nevada, California and Mexico.[14]Pinyon-juniper and riverside woodlands may be used locally where available.[24] The white-breasted nuthatch is the only North American nuthatch usually found in deciduous trees; red-breasted, pygmy and brown-headed nuthatches prefer pines or other conifers.[16]
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 also provide edible seeds.[14] White-breasted nuthatches seldom excavate their own nest holes like red-breasted nuthatches.[3] Although suitable habitat is distributed continentally, it is discontinuous. The separate populations of thisnon-migratory species have diverged to form distinct regional subspecies.[25]
The white-breasted 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,[26] and this species has occurred as a vagrant toVancouver Island,Santa Cruz Island, andBermuda. One bird landed on theRMSQueen Mary six hours' sailing east ofNew York City in October 1963.[14]
The white-breasted nuthatch often travels with smallmixed flocks in winter. These flocks are led bytitmice and chickadees, with nuthatches anddowny woodpeckers as common attendant species. Participants in such flocks are thought to benefit in terms offoraging 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.[27]
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The white-breasted nuthatch ismonogamous, 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.[26] 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.[28] The nest cavity is usually a natural hole in a decaying tree, sometimes an oldwoodpecker nest.[14]
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 thealtricial chicksfledge in a further 18 to 26 days.[15] 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 itsfeces 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.[14]
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Like other nuthatches, the white-breasted nuthatch is a noisy bird with a range of vocalizations. The male's mating song is a rapid nasalqui-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 squeakynit, uttered up to 30 times a minute. A more distinctive sound is a shrillkri repeated rapidly with mounting anxiety or excitementkri-kri-kri-kri-kri-kri-kri-kri; the Rocky Mountains andGreat Basin subspecies have a higher, fasteryididitititit call,[14] and Pacific birds a more nasalbeeerf.[16]
The white-breasted nuthatch forages along tree trunks and branches in a similar way to woodpeckers andtreecreepers, 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.[29][30]
The white-breasted nuthatch isomnivorous, eatinginsects and seeds.[31] 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.[26] 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 aspine weevils,oystershell and otherscale insects, andjumping plant lice.[28][32][33] This bird will occasionally feed on the ground, and readily visits feeding stations for nuts, suet andsunflower seeds, the last of which it often takes away to store.[26] The white-breasted nuthatch was also observed visiting raccoon latrines in order to find seeds.[34]
Predators of adult nuthatches include owls anddiurnalbirds of prey (such assharp-shinned andCooper's hawks), and nestlings and eggs are eaten by woodpeckers, smallsquirrels, and climbing snakes such as thewestern rat snake. The white-breasted nuthatch responds to predators near the nest by flicking its wings while makinghn-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.[28] The nuthatch may also smearblister 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.[35] The estimated average lifespan of the white-breasted nuthatch is two years,[28] but the record is twelve years and nine months.[26]
The white-breasted 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 ahouse wren, which destroys eggs.[36] 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.[36]
The white-breasted nuthatch can be a host for certain parasites such as theprotistsLeucocytozoon orTrypanosoma.[37] The white-breasted nuthatch is the typical host of another protist species,Haemoproteus sittae.[38]Trematodes, such asCollyriclum faba, have also been recorded in this species.[39] The white-breasted nuthatch can also be the target ofhematophagous flies of the familyHippoboscidae, such asOrnithoica confluenta andOrnithomya anchineuria[40][41][42] or of certainmites, such asKnemidokoptes jamaicensis, which produces scabies.[43]
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The white-breasted nuthatch is a common species with a large range, estimated at 8,600,000 km2 (3,300,000 sq mi). 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 (fewer than 10,000 mature individuals) or the population decline criterion (declining more than 30% in ten years or three generations) of theIUCN Red List. For these reasons, the species is evaluated asleast concern by theInternational Union for the Conservation of Nature.[1]
The removal of dead trees from forests may cause problems locally for this species because it requires cavity sites for nesting; declines have been noted in Washington state, Florida, and more widely in the southeastern U.S. west to Texas. In contrast, the breeding range is expanding in Alberta, and numbers are increasing in the northeast due to regrown forest.[14][44][45] The white-breasted nuthatch is protected under theMigratory Bird Treaty Act of 1918, to which the three countries in which it occurs (Canada, Mexico, and the United States) are all signatories.[28]
