White-breasted Nuthatch / agile birds that creep along trunks and large branches, probing into bark furrows with their straight, pointed bills. Like other nuthatches, they often turn sideways and upside down on vertical surfaces as they forage.
White Breasted Nuthatch -- Ive seen these before. Their yank-yank! call is pretty distinctive, but since theyre rather tiny birds (not tiny as in chickadee-size, but still small), I can still have difficulty finding them even if I know theyre there.