One of my reference books swears that flickers will only nest in hollow tree cavities that are 30 to 50 feet above the ground. Evidently the pair that nested here hadn't read that book. They found the nest box I put out in my yard, made from a 4-foot chunk of a hollow tree trunk I had mounted on a post in my yard. I had hoped to attract tree swallows, which I did. But then along came the flickers, who evidently needed a place to nest right away. They chased the swallows away and took over. I set up a blind and enjoyed the show.
jan