Photo © Keith Williams
Photo © H. S. Farm

Growing Up Kestrel

Those who monitor American Kestrel nests know that these petite raptors are feisty and adaptable. But do the young kestrels that grow into handsome little falcons in your nest boxes ever return as adults? Or, do they strike out for parts unknown in some distant corner of the continent? The answers, from a new study in Idaho, may surprise you.

Since most kestrels breed in their first year after hatching, researchers did not have to wait long to see whether the kestrels were leaving home. Perhaps surprisingly, only 4% of the banded nestlings returned to nest in the study area, while the majority dispersed out of the study area. Of those that stayed put, females moved farther than males, about 6 miles (9.8 km) compared to the males’ 3.3 miles (5.3 km). Researchers think that although males are certainly capable of long-distance moves (one kestrel is known to have dispersed more than 1,200 miles!), they typically do not move as far because they need to defend territories. Females, on the other hand, are free to wander and choose the best available mate. Interestingly, juveniles whose parents were raised in the area were three times more likely to stay in the same area than those whose parents were immigrants. Two “local” sons even came back a few years later to nest in the very boxes from which they fledged.

How do American Kestrels compare to American people when it comes to leaving home? According to a 2008 Pew Research Center survey, the percentage of Americans who resided in the same town in which they were born was 37%, compared with just 4% of the studied kestrels remaining in their area of origin. The popular idea that most kestrels stay in the same “hometown” in which they were raised is more likely a reflection of our own human dispersal patterns—people are almost an order of magnitude more likely to stay!

Deciding whether to move or stay always involves tradeoffs. Kestrels leave their hometowns for some of the same reasons people do: to seek out new opportunities, to learn what’s out there, and to start a family. However, those that stay do so for reasons that we can also relate to: the climate is favorable, they know the area, and it’s a good place to raise kids. If you don’t yet have a kestrel nesting box available in your area, why not provide one in case this beautiful little falcon finds its way to your hometown?

Reference: Steenhof, K., and J. A. Heath. 2013. Local recruitment and natal dispersal distances of American kestrels. The Condor 115(3):584-592.