Certhiidae - Treecreepers
Treecreepers are small, brown, almost mouse-like birds with a habit of running up (rarely down) tree-trunks. Although they are relatively common, their quiet unobtrusive manners mean they often go undetected. Treecreepers have strong legs and feet, with long, deeply curved claws, stiffened tail feathers (which are used for support) and a fine down-curved bill. They mostly search for insects hidden under bark or in little crevices in the trunk. Intriguingly, bill and claw length of individuals does vary significantly between the seasons, which is thought to be an adaptation to maximise foraging efficiency.