Two White-breasted Nuthatches were flying around our backyard, and from their behavior I think they were involved in some courtship rituals.
Suddenly the bird on the right, a female probably, leaned on the branch as if she was going to sleep.
But only a second later she was up.
The pair continued to fly around together and spent a lot of time running up and down the trunk of an oak tree.
Later on, the female landed on our deck railing and rolled over, shaking her feathers. I thought she was struck with something and was dying. I ran out, and she flew back to the oak tree to find her mate. You can say that I still have to learn a great deal about bird courtship.