The woodcreepers are generally fairly uniform in appearance. They range in size from the wedge-billed woodcreeper (13 cm (5.1 in)) to the strong-billed woodcreeper (35 cm (14 in)). Males tend to be slightly larger than females on average, but considerable overlap in size occurs in most species. Pronounced sexual dimorphism in size and plumage is rare. Bill size and shape accounts for much of the variation between the species. Bills can be straight or highly decurved, and can account for as much as a quarter of the length of the bird (as happens in the long-billed woodcreeper). The plumage is usually subdued and often brown, or sometimes rufous or other dark colours. Many species have patterns such as checking, spotting, or barring on their plumage. The feathers of the tail are rigid and are used for supporting the body when climbing tree trunks the tail can support most of the body weight and birds that lose their tail find climbing difficult. Woodcreepers climb by flexing their legs and hopping up the trunk. The feet of the woodcreepers are also modified for climbing. The front toes are strongly clawed and toe IV is as long as toe III to increase the ability of the bird to grasp around branches. The legs are short but strong. Woodcreepers are also characterized by a belly feather growth pattern not found in any other birds.