Certhiidae – Treecreepers

The treecreeper, Certhiidae are a family, of small passerine birds, widespread in wooded regions of the Northern Hemisphere and sub-Saharan Africa. The family contains just nine species in one genus, Certhia. Their plumage is dull-coloured, and as their name implies, they climb over the surface of trees in search of food; usually, like the Eurasian Treecreeper, working their way around and up a trunk before flitting down to the foot of another.

Most species of treecreeper occur in the Palearctic and Indomalaya ecozones, from Western Europe to Japan and India. One species occurs in North America from Alaska to Nicaragua. All species of treecreeper are found in forest and woodland habitats. The more northerly species are partly migratory, and those found in warmer climates are thought to be resident, although information is lacking for many species.

They measure from 12 to 18 centimetres in length. Their bills are gently down-curved and rather long, used for probing bark for insects and spiders. They often climb up tree trunks in a helical path, hopping with their feet together; their toes are long and tipped with strongly curved claws for gripping. Their tails are stiffened to use as a prop while climbing, unlike those of their closest relatives, the newly split Salpornithidae (Spotted creepers), which are shorter and not stiffened. Their songs and calls are thin and high-pitched.

Eurasian Treecreeper Certhia familiaris – ©Ashley Beolens

Treecreepers are generally unobtrusive and are often indifferent to humans. They occur as singles or in pairs, sometimes in small family groups after fledging. Occasionally they will flock with other passerines in winter to forage. Communal roosting has been observed in three species (and may occur in more), with as many as 20 birds sharing a roosting hole behind loose bark in order to conserve warmth.

They forage on the trunks of large trees, moving up the trunk in a progression of small hops. They then fly to the bottom of another tree, climbing it in a spiral fashion searching for prey. The majority of their diet is composed of small invertebrates, including insects and their larvae, spiders, and pseudoscorpions. In hard times seeds and fruits may be taken, and a few species will also visit birdfeeders.

Short-toed Treecreeper Certhia brachydactyla – ©Dubi Shapiro

The Certhiidae are monogamous and territorial. Nests and eggs vary between the genera but they are all monogamous and both sexes parent. They usually nest in a gap between the tree bark and the tree, but if such sites are not available, they will use special nestboxes, a knothole or abandoned woodpecker nest-hole, whereas the nests of the Salpornithidae are placed in the fork of a branch. Three to six white eggs speckled with reddish brown dots are laid an incubation lasts around two weeks, and young fledge another two weeks or so. The females incubate and are fed by the males.

Forest habitats everywhere are under pressure from humans and wildfires, but only one treecreeper species has a small enough range that the loss of its temperate forest habitat has caused conservation concerns – the Sichuan Treecreeper Certhia tianquanensis, which is limited to very few forest patches in the mountains of Sichuan, China, where development and disturbance are pressing concerns.