I'm not a bird expert but I have learned some about them in taking pictures of them to put on calendars for my "bird loving" friends. One of the birds I have learned the sound they make is the Red-Bellied Woodpecker. I heard the pecking sound. Then the vocal shrill. I followed it and spotted the bird in one of our trees that has a dead limb in it.
I watched the bird go into a hole in the limb and then stick it's head out.
I conclude that there must be a nest. I do a little research to see when they lay eggs and how long before they hatch.
I took the these photos with a 300mm lens. I couldn't get close enough or at the right angle to see into the hole when the bird wasn't there.
I watched it. Then I didn't see the woodpecker anymore. I think something may have happened to the eggs. I was sure hoping I would see babies.
Have a good one!