American kestrels are small falcons often seen on utility lines in open country. From that height they hunt small mammals and insects, sometimes hovering over their prey before striking.
Kestrels nest in cavities. Because of a shortage of natural tree cavities, the Madison Audubon Society has built about 40 kestrel nest boxes in Columbia and Jefferson counties.
Kestrel nest boxes should be mounted 15-20 feet high. Ideally the entrance hole faces southeast to absorb the sun's warmth and avoid strong winds.
Kestrels migrate south for the winter. That means nest boxes must be cleaned before the birds return to Wisconsin in spring.
Cleaning out a nest box requires two people. Here Brand loosens the bottom bolt so we can pivot the tall post to the ground.
With the post now pivoted to the ground, we open the side of the box and inspect its contents. If we see a nest of sticks over the existing wood chips, it usually means a starling used the nest box.
Kestrels add no material to the box, and after nesting leave behind no egg membranes or shells. Here Brand examines the box for "whitewash," or feces, a sign that kestrels used the box the previous season.
In this box we find only matted sawdust, indicating the box was used by a kestrel.
In another box we find bloodstains, probably from dismembered prey the kestrels brought inside to feed their chicks.
Kestrels prefer sawdust or wood chips in nest boxes. Those materials mimic a natural cavity in a tree snag.
Once the box is emptied and scraped clean, Brand puts 3-4 inches of fresh wood chips inside. The side of the box is closed by a wire wrapped around nails.
Because it takes two people to pivot the post up and down, we have no photos of that step. After raising the post, we're ready to tighten the bottom bolt.
Another nest box ready for the spring arrival of a kestrel!
