Four species live in North America (White-breasted, Red-breasted, Pygmy, and Brown-headed), and even though they do not take to nesting boxes as well as some other birds, they are cavity-dwelling birds and are worth trying to attract. 

Their name comes from their habit of pushing a nut into a crevice in the bark of a tree, and then pounding it, appearing to try to "hatch" it.

White-breasted Nuthatch

The White-breasted Nuthatches (Sitta carolinensis) are found in nearly all states in beeches and oaks in the east, and in oaks and conifers in the west. They have black caps over white faces, with gray backs, short tails, and long, narrow bills. With no great musical talent, these birds give a call that is nasal sounding, either a rapid series of whistles on one pitch, or a one low nasal note. This bird is more widespread and more common at feeders than its red-breasted cousin.  It can even be taught to eat from human hands.

This nuthatch feeds on insects gleaned from the bark of tree trunks and the nuts of deciduous trees. It loves acorns and beechnuts and also likes pine seeds, grain waste, and the seeds and berries of other plants. It stores food in the fall under loose tree bark. At feeders it likes sunflower seeds, suet, peanut butter, nutmeats, and cracked corn and millet.

Red-breasted Nuthatch

The Red-breasted Nuthatch (Sitta canadensis) is slightly smaller, with a distinctive black stripe across the eye and a rust-colored breast. It is also a bird of the forest, preferring conifers or mixed woods in nearly every part of the country. It digs a hole in soft, decaying wood and smears the entrance hole with pitch. They are messy nest-builders, so don't open the nesting box while it is occupied, or it may all fall out.