Common treecreeper, Treecreeper
The Eurasian treecreeper (Certhia familiaris) is a small woodland bird with cryptic plumage and a quiet call. It can be most easily distinguished from the similar Short-toed treecreeper, which shares much of its European range, by its different song. In the British Isles, where it is the only living member of its genus, this bird is simply known as treecreeper.
Eurasian treecreepers have warm brown upperparts intricately patterned with black, buff, and white, and a plain brown tail. Their belly, flanks, and vent area are tinged with buff. The sexes are similar, but the juvenile has duller upperparts than the adult, and their underparts are dull white with dark fine spotting on the flanks. Treecreepers have long decurved bills and long rigid tail feathers that provide support as they creep up tree trunks looking for insects.
Eurasian treecreepers breed across the Palearctic from Ireland to Japan. They prefer mature trees and are found mainly in coniferous forest, especially spruce and fir. However, in European Russia, or the British Isles, these birds frequent broadleaved or mixed woodland in preference to conifers. They are also found in parks and large gardens. Eurasian treecreepers are non-migratory in the milder west and south of their breeding range, but some northern birds move south in winter, and populations that breed on mountains may descend to a lower altitude in winter.
Eurasian treecreepers are energetic birds that are easily overlooked as they hop mouse-like up a vertical trunk, progressing in short hops, using their stiff tail and widely splayed feet as support. They are not wary and are indifferent to the presence of humans. They have a distinctive erratic and undulating flight, alternating fluttering butterfly-like wing beats with side-slips and tumbles. Migrating birds may fly by day or night. Eurasian treecrepers are solitary in winter, but in cold weather up to a dozen or more birds will roost together in a suitable sheltered crevice. Eurasian treecreepers usually forage on tree trunks, starting near the tree base and working their way up using their stiff tail feathers for support. They do not come down trees head first but fly to the base of another nearby tree. They use their long thin bill to extract insects from crevices in the bark. Eurasian treecreepers usually spend time in trees, but they may also hunt prey items on walls, bare ground, or amongst fallen pine needles. Females forage primarily on the upper parts of the tree trunks, while the male uses the lower parts. Eurasian treecreepers may sometimes join mixed-species feeding flocks in winter. The contact call of these small birds is a very quiet, thin and high-pitched 'sit', but the most distinctive call is a penetrating 'tsree', with a vibrato quality, sometimes repeated as a series of notes. The male's song begins with 'srrih, srrih' followed in turn by a few twittering notes, a longer descending ripple, and a whistle that falls and then rises.
Eurasian treecreepers are carnivores (insectivores). They feed on various insects and spiders and may add some conifer seeds to their diet in the colder months.
Eurasian treecreepers are monogamous and form pairs. They nest in tree crevices or behind bark flakes favoring giant sequoia as a nesting tree, since a nest cavity can be easily hollowed out in its soft bark. Crevices in buildings or walls are sometimes used, and artificial nest boxes or flaps may be preferred in coniferous woodland. The nest has a base of twigs, pine needles, grass or bark, and a lining of finer material such as feathers, wool, moss, lichen, or spider web. In Europe, the typical clutch is 5-6 eggs and is laid between March and June, but in Japan 3-5 eggs are laid from May to July. The eggs are white with very fine pinkish speckles mainly at the broad end. The female incubates the eggs alone for 13-17 days until the altricial downy chicks hatch; they are then fed by both parents, but brooded by the female alone, for a further 15-17 days to fledging. The young return to the nest for a few nights after fledging and start to breed from the age of one year.
Although Eurasian treecreepers are common through much of their range, they are rare in the northernmost areas. These small birds are vulnerable to hard winters, especially if their feeding is disrupted by an ice glaze on the trees or freezing rain.
According to the IUCN Red List, the total population size of the Eurasian treecreeper is 40,000,000-76,000,000 mature individuals. In Europe, the breeding population consists of 6,050,000-11,400,000 pairs, which equates to 12,100,000-22,700,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
As Eurasian treecreepers feed on a wide variaty of insect and arthropod populations, they help control their populations and thus help reduce arboreal pests. When treecreepers consume the seeds during winter, they may also help disperse them throughout the forests.
