Thursday, March 24, 2016

American Kestrels use Tucson Audubon Nest Box

Male American Kestrel near the nest box with a lizard
Tucson Audubon has an experimental nest box program to see what Sonoran Desert birds will use nest boxes in the Tucson metro area. We want to find out which species will attempt to nest in boxes and if their nesting attempts are successful.

Five kestrel eggs in the box
Conventional wisdom in this area has been that nest boxes might get too hot here in the desert. However, in the last three springs we have had successes with Western Screech-Owl, Ash-throated Flycatcher and Brown-crested Flycatcher. Birds have a higher body temperature and can withstand fairly hot ambient temperatures. In additional, many of these species nest early in the spring here, when temperatures are not as high. More about our nest box program is at

To date, however, boxes we have promoted for American Kestrels have so far gone unused. Until now!

It is not too surprising that we have not had a kestrel nesting attempt so far. While there are a lot of kestrels in our area in the winter, fewer stay to nest. And we have relatively few boxes up for them so far.

But since early March a pair of kestrels has been seen regularly in the vicinity of one of the boxes, on Tucson's northwest side. They have been seen sharing food (lizards) and mating.

Close up of eggs
On March 24 we checked the nest box and found five eggs! The eggs fit the description of kestrel eggs in Birds of North America Online. And according to BNA, normal clutch size is 4-5 eggs. They typically hatch around 30 days after laying.

Kestrel box, on a wall about 9' high
We don't know when they were laid but we will be checking the box regularly. We have started a nesting attempt record at Their instructions suggest checking the nest every 4-5 days.

We will update you regarding the status of this nest! Wish them luck!

Male with a lizard with female nearby
(apparently they eat a lot of lizards)

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