Sittidae

Sittidae is a family of small passerine birds which has two subfamilies

Sittinidae, which contains the single genus Sitta containing about 24 species of nuthatches, which are found across Eurasia and North America.
Tichodromadinae, which contains one species, the Wallcreeper, Tichodroma muraria, which is restricted to the mountains of southern Eurasia.

The Wallcreeper is intermediate in its morphology between the nuthatches and the treecreepers, but its appearance, the texture of its plumage, and the shape and pattern of its tail suggest that it is closer to the former taxon. It is occasionally placed in a separate family, the Tichodromadidae.

Taxonomy

The Sittidae family was described by René-Primevère Lesson in 1828. Its closest relatives are the treecreepers, and the two families are sometimes placed in a larger grouping with the wrens and gnatcatchers. This superfamily, the Certhioidea is proposed on phylogenetic studies using mitochondrial and nuclear DNA, and was created to cover a clade of four families removed from a larger grouping of passerine birds, the Sylvioidea.

The Nuthatch Vanga of Madagascar and the sitellas from Australia and New Guinea were once placed in the family Sittidae, because of similarities in appearance and lifestyle to the nuthatches, but they are not closely related, the resemblances arising from convergent evolution to fill an ecological niche.

Behaviour

Breeding

All the species in this group nest in cavities. The Wallcreeper and two nuthatches, the Western and Eastern Rock Nuthatches use rock crevices, and the rest of the nuthatches nest in tree holes. The chicks are altricial, which means they are blind, featherless and helpless at birth. Both parents feed the nestlings until the young birds fledge.

Feeding

The Wallcreeper is an insectivore, which feeds on invertebrates, primarily insects and spiders gleaned from the rock face. Invertebrates are also a major part of the diet for nuthatches, especially during the breeding season, but most species also eat seeds at least during the winter, when invertebrates are less readily available. Larger food items, such as big insects, snails, acorns or seeds may be wedged into cracks and hacked with the nuthatches's strong bill, this of course being the behaviour which gives that subfamily group its name. The nuthatches all store food, usually seeds, which may be pushed into crevices or into the ground, hidden under small stones, or tucked behind bark flakes; the rock nuthatches will also wedge snails into suitable crevices for consumption in times of need. Caches are recovered by memory, and can be retrieved as long as 98 days after being stored. In one study of European Nuthatches birds refrained from using their caches during benign conditions in order to save them for harsher conditions.

Fossils

The fossil record for this group appears to be restricted to a foot bone of an early Miocene bird from Bavaria which has been identified as an extinct representative of the climbing Certhioidea, a clade comprising the treecreepers, Wallcreeper and nuthatches. It has been described as Certhiops rummeli.

Status

The Wallcreeper and most nuthatches have large populations and extensive geographical ranges, and present few conservation problems,

A few of the more restricted nuthatch species are threatened by deforestation.

the White-browed Nuthatch is endangered The population of a few thousand birds is decreasing, and no conservation measures are in place.
The endangered Algerian Nuthatch occurs only at four known sites in Algeria, and it is possible that the total population does not exceed 1,000 birds.
The Yunnan Nuthatch is vulnerable, although still locally common.
The Yellow-billed Nuthatch is vulnerable especially on Hainan, where more than 70% of the woodland has been lost in 50 years.
The Krüper's Nuthatch is near-threatened in its stronghold in Turkey, where urbanisation and development for tourism are placing considerable pressure on mature coniferous forest.