The treecreepers are a family, Certhiidae, of small passerinebirds, widespread in wooded regions of the Northern Hemisphere and sub-Saharan Africa. Their plumage is dull-coloured, and as their name implies, they climb over the surface of trees in search of food. Treecreepers 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.