We were recently contacted by a gentleman named Rich Carpenter about a different style of kestrel box that he's used on his property for about twenty years. Rather than the wood most nest boxes are built from, Rich's "boxes" are built from sections of galvanized steel sheet metal 12" round furnace duct pipe painted light gray or light tan. He reports that the boxes are lighter, easier to maintain, more durable, and cheaper to construct than the wood boxes he used previously. Though he originally designed the metal boxes for Wood Ducks, he reports that both American Kestrels and Eastern Screech-owls have also successfully nested in them.
Rich reports that he lives in an area where it's not uncommon to have a week of temperatures in the 90s during the day and occasionally as high as the low 100s, but he reports that he's never lost a chick to overheating. The design might not work for those living in areas with extreme heat or extreme cold, and it's also worth noting that boxes placed in wood duck habitat are likely getting more shade than those purpose-installed for kestrels. But we certainly wanted to share his design in case anyone in the proper climate might want to give Rich's design a try.
If anyone has ideas on how to alter these boxes to make them more kestrel-specific, or has tried something similar and can provide feedback, we'd love to hear it.