Tufted Titmouse, Baeolophus bicolor
My first two pictures of this attractive species, common throughout eastern North America but not found where I live in California, came on springtime visits four years apart to Cape Cod and its very birdy Beech Forest refuge just outside of Provincetown. Above, a classic pose; below, an incubating female away from the nest, showing her brood patch, the breach in her belly feathers that allows her to keep her eggs warm by direct contact with her skin. Birds of North American Online reports that only the female of this species incubates, and that she often leaves the nest in response to the call of the male, who feeds her off-nest.
The sexes aren't distinguishable by plumage, but this one was singing, and so identifying himself as a male, in Ohio's Shawnee Forest in April 2015.