The White-breasted Nuthatch (Sitta carolinensis) is a member of the family Sittidae, within the Order Passeriformes.  They go down trees head first, gleaning for insects and other arthropods. Seeds also play a large part in their diet and they readily come to bird feeders.  When a threat, such as a squirrel approaches their nest, they flare their wings out to look larger and more intimidating, as in the pictures below.