Nuthatch
2008/9 Schools Wikipedia Selection. Related subjects: Birds
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 Male Eurasian Nuthatch
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The nuthatches are a family, Sittidae, of generally very similar small passerine birds found throughout the Northern hemisphere.
Most nuthatches are woodland birds, although a few species have adapted to rocky habitats. They have the unusual ability to climb down trees head first, unlike species such as woodpeckers which can only go upwards.
Nuthatches have big heads, short tails and powerful bills and feet. Their shape is distinctive, and all species are recognizable as nuthatches if one has been seen.
They are generally omnivorous, eating mostly insects, nuts and seeds. Most are resident, but the Red-breasted Nuthatch migrates from the north of its range.
Nests are in holes or crevices. In some species the size of the hole is reduced by the building of a mud wall. The Eurasian Nuthatch includes in its song repertoire a single high pitched note that it repeats often from a high vantage point.
This group gets its name from the habit of the Eurasian Nuthatch of wedging a nut in a crevice in a tree, and then hacking at it with its strong bill.
Taxonomy
The nuthatches are all placed in the single genus Sitta (Linnaeus, 1758), the genus name being derived from Greek sitte, "nuthatch". Their nearest relative relative is the Wallcreeper, Tichodroma muraria, which in the past was sometimes considered to be the only representative of the subfamily Tichodromadinae of the nuthatch family, Sittidae, with the "true" nuthatches constituting the subfamily Sittinae; it is more usual now for the Wallcreeper to be separated in its own family, Tichodromadidae.
Species boundaries may be difficult to define; the North American Red-breasted Nuthatch, Corsican Nuthatch and Chinese Nuthatch have breeding ranges separated by thousands of kilometres, but are similar in habitat, appearance and song. They were formerly often considered to be one species, but are now invariably split as three. Together with Kruper's and Algerian Nuthatch, they form a superspecies, the members of which all excavate their own nests as well as showing resemblances in plumage and vocalisations.
The Eurasian, Chestnut-vented, Kashmir and Chestnut-bellied Nuthatches form a superspecies replacing each other in various parts of Asia. They have been regarded as anything from one to four species, with the latter being the current view. However, a recent proposed further split is that of Chestnut-bellied Nuthatch into the Indian Nuthatch Sitta castanea, found south of the Ganges, and Chestnut-bellied Nuthatch sensu strictu, S. cinnamoventris of the Himalayas.
A 2006 review of Asian nuthatches suggested that there are still unresolved problems in nuthatch taxonomy. Proposals include raising the white-breasted northern subspecies of Eurasian Nuthatch, S. (e.) artica to full species status, and splitting the genus Sitta. The latter suggestion would move the red- and yellow-billed south Asian species ( Velvet-fronted, Yellow-billed and Sulphur-billed Nuthatches) to a new genus, create a third genus for Blue Nuthatch, and possibly a fourth for Beautiful Nuthatch.
The species diversity for this family reaches is greatest in southern Asia, where about 15 species occur, but it has representatives across much of the Northern Hemisphere. The currently recognised nuthatch species are tabulated below.
| Species in taxonomic order | |||
| Common name | Binomial | Range | Image |
|---|---|---|---|
| Eurasian Nuthatch | Sitta europaea | Temperate Eurasia |  |
| Chestnut-vented Nuthatch | Sitta nagaensis | NE India east to NW Thailand |  |
| Kashmir Nuthatch | Sitta cashmirensis | E Afghanistan to W Nepal | |
| Chestnut-bellied Nuthatch | Sitta castanea | Four races found in the foothills of the Himalayas from NE India to W Yunnan and Thailand have been proposed as a separate species from the nominate form which breeds in N and C India. |  |
| White-tailed Nuthatch | Sitta himalayensis | Himalayas from NE India to SW China, locally east to Vietnam |  |
| White-browed Nuthatch | Sitta victoriae | Endemic to Burma. | |
| Pygmy Nuthatch | Sitta pygmaea | W North America from British Columbia to SW Mexico |  |
| Brown-headed Nuthatch | Sitta pusilla | SE US, Bahamas |  |
| Corsican Nuthatch | Sitta whiteheadi | Endemic to Corsica | |
| Algerian Nuthatch | Sitta ledanti | Endemic to NE Algeria | |
| Krüper's Nuthatch | Sitta krueperi | Turkey, Georgia, Russia and on the Greek island of Lesvos. |  |
| Snowy-browed Nuthatch or Chinese Nuthatch | Sitta villosa | China, North Korea, and South Korea | |
| Yunnan Nuthatch | Sitta yunnanensis | Endemic to SW China | |
| Red-breasted Nuthatch | Sitta canadensis | W and N temperate North America, winters across much of the US and southern Canada |  |
| White-cheeked Nuthatch | Sitta leucopsis | E Afghanistan to W Nepal, W China |  |
| White-breasted Nuthatch | Sitta carolinensis | North America from S Canada to Mexico |  |
| Western Rock Nuthatch | Sitta neumayer | The Balkans east through Greece and Turkey to Iran |  |
| Eastern Rock Nuthatch | Sitta tephronota | N Iraq, W Iran east through Central Asia |  |
| Velvet-fronted Nuthatch | Sitta frontalis | India and Sri Lanka through Southeast Asia to Indonesia |  |
| Yellow-billed Nuthatch | Sitta solangiae | Vietnam and Hainan Island, China | |
| Sulphur-billed Nuthatch | Sitta oenochlamys | Endemic to the Philippines | |
| Blue Nuthatch | Sitta azurea | Malaysia, Sumatra and Java | |
| Giant Nuthatch | Sitta magna | China, Burma, and Thailand. | |
| Beautiful Nuthatch | Sitta formosa | NE India, Burma locally in S China and northern SE Asia |  |
Description
The Nuthatches are compact birds with a sturdy, long, straight and pointed bill. They have short legs with strong toes and long claws, short wings, and short square 12-feathered tails. The back is typically blue-grey (violet-blue in some east Asian species) and the underparts are white variably tinted with buff, orange, rufous or lilac. The head bears a long black eye stripe, and sometimes a white supercilium or dark cap. The sexes are similar, but differ in the underpart colouration, especially on the rear flanks and under the tail. Juveniles and first-year birds are very similar to adults, and may be impossible to age.
Nuthatches range in size from the Giant Nuthatch, 195 mm (7.75 in) long and weighing 36–47 g (1.3–1.6 oz) to the Brown-headed Nuthatch 105 mm (4 in) long and weighing 10.2 g (0.36 oz), but all are immediately recognisable as members of the same family.
Nuthatches are typically very vocal, with an assortment of whistles, trills and calls, but their songs tend to be simple, and often identical to the calls.
Distribution and habitat
Representatives of the nuthatch family occur in suitable habitat in most of North America and Europe, and through Asia down to the Wallace Line. The group has a toehold in North Africa through the the endemic Algerian Nuthatch in a small area of north-east Algeria, and a population of the Eurasian Treecreeper subspecies S. e. hispaniensis in the mountains of Morocco. Most species are resident year-round, the only significant migrant being the Red-breasted Nuthatch, which winters widely across North America, deserting the northernmost parts of its breeding range in Canada. It has occurred as vagrant to Bermuda, Iceland and England.
Most nuthatches are woodland birds, the preferred tree types varying from species to species, although the majority of nuthatches are found in conifer or other evergreen forests. The strength of the association varies from Corsican Nuthatch's close link with Corsican Pine to the catholic habitat choice of the Eurasian Nuthatch, which prefers deciduous or mixed woods, but breeds in coniferous forests in the north of its extensive range. Two species are not strongly tied to woodland; as their names imply the two rock nuthatches breed on rocky slopes or cliffs, although both will move into wooded areas when not breeding.
Nuthatches typically prefer a fairly temperate climate, and most of the species breeding in the more southerly regions of the northern hemisphere are found in highland habitats. Those that breed further north may be lowland birds in the north of their range, but associated with mountains further south. Thus, the Eurasian Nuthatch, which breed within the 16-27oC isotherm, is found only between 1,750 and 1,850 m (5,700–6,100 ft) altitude in Morocco. The only member of the family for which the preferred habitat is tropical lowland forests is the Velvet-fronted Nuthatch.
Behaviour
Breeding
Nuthatches are monogamous and pair for life. They nest in cavities, normally tree holes except in the case of the two rock nuthatches, and make a simple cup with softer materials to receive the eggs, which are white eggs with coloured (usually red or yellow) markings. The clutch size varies, with northern species tending to lay more eggs. The eggs are incubated by the female alone or both sexes for between 12 and 18 days, with another 21–27 days until the young can fly. Both sexes feed the young, and in the two small American species, Brown-headed and Pygmy, young males from the previous year also assist with feeding.
The five species in the Red-breasted Nuthatch superspecies excavate their own tree holes whereas other species use natural holes or old woodpecker nests. Several species reduce the size of the entrance to the nest hole and seal up cracks with mud. Two American nuthatches have other nest defences. The Red-breasted Nuthatch daubs sticky conifer resin globules around the entrance to its nest hole, the male applying the resin outside, and the female inside. It is thought that resin may deter predators or competitors. The resident birds avoid the resin by diving straight through the hole. White-breasted Nuthatches smear blister beetles around the entrance to the nest. It has been hypothesised that the unpleasant smell from the crushed insects deters squirrels, the chief competitor for natural tree cavities.
Western Rock Nuthatch builds an elaborate flask-shaped nest from mud, dung and hair or feathers in a rock crevice, cave, under an overhang on a cliff or on a building. and may push decorative items into crevices and cracks near the entrance to the nest. Its eastern counterpart also heavily plasters the entrance to a cavity, which will be enlarged by the pair if necessary.
Predators of nuthatches are those typical of small woodland birds including accipiters, owls, squirrels and woodpeckers. For those few species for which the data is available, the average lifespan in the wild is between 2 and 3.5 years, although ages of up to 10 years have been recorded. The Eurasian Nuthatch has an adult annual survival rate of 53%.
Cold can be a problem for non-migratory small birds, and several species will form communal roosts in winter. 170 Pygmy Nuthatches have been recorded in a single roost, and this species also engages in controlled hypothermia, lowering its body temperature while roosting to reduce its metabolic rate and conserve energy.
Feeding
Nuthatches typically forage on tree trunks and branches, but unlike woodpeckers and treecreepers they do not use their tails as additional support against the trunk, instead relying on their strong legs and feet to progress. They are able descend head-first and hang upside down beneath twigs and branches. the rock nuthatches are similar in their behaviour, but forage on rock faces and sometimes buildings. When breeding, a pair will feed within its territory, but will readily join mixed-species feeding flocks at other times.
Insects and other invertebrates are a major part of the diet, especially during the breeding season, when the diet may be almost exclusively live prey, but most species also eat seeds at least during the winter months when invertebrates are less readily available. An unusual example of tool use by a bird is the Brown-headed Nuthatch's utilisation of a piece of tree bark as a lever to pry up other bark flakes to look for food. It may carry the bark tool from tree to tree, or to cover a seed cache. As far as is known, all nuthatches store food, usually seeds, but the rock nuthatches will also wedge snails into suitable crevices for consumption in times of need.
Bigger food items, such as large insects, acorns or seeds may be wedged into cracks and hacked with the birds strong bill, this of course being the behaviour which gives this group its name.
Status
Some nuthatches, like the Eurasian Nuthatch and the North American species, have large populations and extensive geographical ranges, and present few conservation problems. In contrast, some of the more restricted species face severe pressures. The endangered White-browed Nuthatch is known only from the Mount Victoria area of Burma, where forest up to 2,000 m (6,560 ft) has been almost totally cleared and habitat between 2,000–2,500 m (6,560–8200 ft) has been heavily degraded. The population of a few thousand birds is decreasing, and no conservation measures are in place..
The Algerian Nuthatch occurs only at four known sites in Algeria, and it is possible that the total population does not exceed 1,000 birds. Fire, grazing by livestock, disturbance and erosion have reduced the quality of the habitat, despite it being in a national park.
Deforestation has also caused population declines for the vulnerable Yunnan Nuthatch and Yellow-billed Nuthatch. The former species has a preference for open pine woodland, and is better able to cope with tree felling, but although still locally common, it has been lost from several of the areas in which it was recorded in the early 20th century. The threat to Yellow-billed is particularly acute on Hainan, where more than 70% of the woodland has been lost in 50 years. Shifting cultivation and use of wood for charcoal-making or fuel are intensifying after Chinese government re-settlement programmes.
A threat of a different kind faces Krueper's Nuthatch in Turkey, where urbanisation and development for tourism are placing considerable pressure on mature coniferous forest, particularly in the coastal areas where the species was once numerous. A law for the promotion of tourism came into force in Turkey in 2003, further exacerbating the threat from habitat loss.