Nuthatches are small, robust birds that belong to the genus Sitta, part of the family Sittidae. These birds are noticeable for their large heads, short tails, powerful bills, and feet—features adapted for their acrobatic foraging habits that often involve scaling tree trunks and branches in various orientations, including upside-down. They display grey or bluish upperparts with some species having a distinctive black eye stripe. Most are found in temperate or montane woodlands of the Northern Hemisphere, but they also inhabit drier and warmer regions in Eurasia. Nuthatches are largely non-migratory, although the North American red-breasted nuthatch travels to warmer areas in winter. They are omnivores, eating insects, nuts, and seeds, often caching food to consume later. Their breeding behaviors range from using natural cavities and old woodpecker nests to reducing hole sizes and sealing entrances with mud for protection. Several species live in threatened habitats, facing risks from deforestation and development, like the endangered white-browed nuthatch in Burma and the vulnerable Yunnan and yellow-billed nuthatches. Despite the conservation challenges faced by some species, others possess substantial populations with minimal threats. The nuthatch's name comes from their unique practice of using their strong bills to wedge food items into crevices and hacks at them. Their taxonomy has been debated, but the family Sittidae is widely recognized and detailed phylogenetic studies suggest they are closely related to treecreepers. There's even historical confusion with other unrelated birds due to convergent evolution, such as the nuthatch vanga and the sittellas. Species boundaries can be complex within the nuthatches, with varying degrees of similarity across different species, and there is continued discourse on how to classify them accurately.