Today I saw a White-breasted nuthatch climbing up a tree in my front yard. They are more common in the winter, but I occasionally see them in the summer. Once in a while I see Red-breasted nuthatches too, but not as often. They’re known for their ability to climb up & down trees head 1st. I have never seen a Pigmy nuthatch or a brown-headed nuthatch, but I’ve seen a Brown creeper once. (Creepers are closely related to nuthatches.) There are actually a couple dozen species of nuthatches & creepers in the world, but hardly any of them live in North America. The link has a list of all the nuthatches & creepers that live in the world compared to the ones that live in the U.S.: http://www.birdpost.com/groups/30.