Corsican nuthatch

Appearance

The adult male is 12 cm long and weighs 11.8–14.4 g . It has a black crown and eyestripe separated by a white supercilium. The upperparts are blue-grey and the throat and underparts are greyish-buff. The flight feathers are dark grey-brown fringed with blue-grey. The bill is black to grey-brown becoming pale grey on the base of the lower mandible, the iris is dark brown and the legs and feet are grey-brown or greyish. The female is similar to the male but has a grey crown and eyestripe. Young birds are duller versions of the adults.

The Corsican nuthatch has a ''pu-pu-pu'' call and a trilled ''hididididididi'' song.

Adults have a complete moult after breeding. Juveniles have a partial moult beginning about 8 weeks after fledging. The adult annual survival rate for male birds is 62 per cent which corresponds to an average lifetime of 2 years and 1 month. The maximum recorded age is 5 years and 7 months.

Distribution

The Corsican nuthatch is a resident bird of the mountain forests of Corsica, and is closely associated with Corsican pine preferably with some very old trees aged 300 years or more for nesting.

Status

The population is about 2,000 pairs; the main threats are fire, which destroys the habitat, and predation by great spotted woodpeckers. Since 2010 this bird is considered as a vulnerable species.

Habitat

The Corsican nuthatch is a resident bird of the mountain forests of Corsica, and is closely associated with Corsican pine preferably with some very old trees aged 300 years or more for nesting.

Reproduction

This territorial species nests in holes in dead and decaying Corsican pines, which are usually self-excavated.

The clutch is typically 4–6 eggs . The eggs are white with red-brown speckles especially at the larger end and are 17.2 mm × 13 mm in size. The female incubates the eggs for 14-17 days until they hatch. She is fed on the nest by the male. The female then broods the altricial downy chicks for the first 8 days. The chicks are fed by both adults and fledge when they are around 20 days old.

Food

During the winter months the diet of the Corsican nuthatch consists almost entirely of seeds from Corsican pines. The birds use their long pointed bills to extract the seeds from mature cones that open in fine weather between November and March. Many of the individual seeds are hoarded by the birds in crevices in the bark. These cached seeds are recovered during bad weather when the cones do not open as unlike crossbills, nuthatches are unable to extract seeds from closed cones. In the spring, during the breeding season, the birds feed mainly on arthropods. In May 1884 when Whitehead opened the gizzards of birds that he had shot, he found that they contained small beetles and other insects.

It has the ability, like other nuthatches, to climb down trees, unlike species such as woodpeckers which can only go upwards, and will also flycatch.

Predators

Predation is an important cause for the breeding failure of the Corsican nuthatch. The most important predator is believed to be the great spotted woodpecker which is relatively abundant in the pine forests. The Corsican nuthatch takes no action to protect its nest from predation unlike other nuthatch species such as the Eurasian nuthatch that reduces the size of the entrance hole with mud or the red-breasted nuthatch that covers the inner surfaces with pine resin. Instead the Corsican nuthatch excavates its own nest and creates only a narrow entrance hole of around 3.2 cm . This compares with the 5–6 cm hole made by the great spotted woodpecker for the entrance to its own nest.

The garden dormouse has been proposed as another possible nest predator. Its small size would allow it to pass through entrance hole of the nest but it is not known to climb high up tree trunks.