creeper, common name for members of a family of small, inconspicuous birds related to wrens and nuthatches. They are found in wooded regions of the temperate Northern Hemisphere. A creeper spirals up a tree trunk using its long, stiff tail as a prop and searches out minute insects with its long, downward-curved beak; it then swoops to the base of another tree to begin again. The most widely distributed member of the family is the brown creeper, Certhia familiaris, found in North America and Eurasia. It is 5 in. (13 cm) long, brown above and white below. Other North American creepers are the Rocky Mt., Sierra, and California creepers. Some warblers are also called creepers, e.g., the honey creeper. Creepers are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes, family Certhiidae.