Kestrel Nest Box Program

Conservation

What started in Iowa in the mid-1800s and ended a few decades later, was a movement that seriously changed Iowa’s landscape. By the early 1920s, a large share of Iowa’s tallgrass prairie and perhaps 75 percent of forestlands had succumbed to the plow and other forms of development. 

Even beyond this peak period of land use change, commercial and residential development has continued to erode away Iowa’s last remaining native prairie and forested land remnants.

Even though the American kestrel remains fairly common, shrinking habitats, clearing of dead trees, and invasions of European starlings have left many struggling to find suitable nesting cavities and forage areas.

Cavity-nesting raptors such as the American kestrel do not build nests of their own.  They rely on natural sites or those created by other birds or animals, including humans. 

Even when hunting habitat and prey are available, the lack of a nest site can be the major reason for the non-productively of an American kestrel species in a given area.

Whenever possible, Iowans should try to preserve the kestrel’s natural habitat from further depletion or become involved in reforestation programs.  Where sites do not currently exist, or have been destroyed, kestrels will gladly accept “pre-fab” homes such as the nest boxes shown in this site. 

You can help maintain or even increase the American kestrel population by installing nest boxes along the roadways in your area of the state.   

Young American kestrels hunting socially after nest departure.

Illustration source: USGS, Northern Prairie Wildlife Resource Center

Origin of the American Kestrel Interstate 

Nest Box Program

In 1983, Ron Andrews of the Iowa Department of Natural Resources originated the interstate nest box program for American Kestrels.

Working in cooperation with the Iowa Department of Transportation, nest boxes were attached to the backs of information signs along the interstate rights-of-way. Twenty nest boxes were placed on signs along I-35 in northern Iowa that first year as an Eagle Scout project, and eight were used by kestrels.

Nest boxes now occur nearly every mile of I-35 from Missouri to Minnesota. This corridor represents the nation's first statewide kestrel trail along an interstate system.

These efforts in Iowa have been coordinated by the Iowa Department of Natural Resources’ Wildlife Diversity Program and implemented at the local level by state wildlife diversity personnel, county conservation board staff, and a host of volunteers. Since the program was started, hundreds of nest boxes have been attached to highway signs elsewhere in Iowa.

Many other states, including Rhode Island, Nebraska, and Idaho, have adopted the kestrel box program.

Working with kestrels along Interstate-35 in Iowa  

American kestrels require open terrain for hunting, and the grassy rights-of-way are ideal for this purpose. While driving the interstate, it is not uncommon to see a kestrel hovering above a right-of-way or perched on a power line searching for prey. The nest boxes are predator-proof because raccoons and other predators are unable to climb the steel posts that support the signs.

In Iowa, nest box use by kestrels averages 50 percent, and young are successfully raised in about 70 percent of these boxes. European starlings occupy most of the boxes not used by kestrels. With an average of three young kestrels raised in each successful kestrel nest box, each year the Iowa program yields about 105 young for every 100 nest boxes in place.

Dan Varland studied the behavior and survival of young kestrels leaving their nest boxes along I-35 for his doctoral research in Animal Ecology at Iowa State University.

Dan followed the young by attaching radio-transmitters to them just before they left their nests. Dan attached transmitters to a total of 61 birds during each of three summers, 1988 - 1990. He found that the young left the interstate right-of-way soon after they could fly and went to nearby areas to hunt and for cover.

Only two of the 16 young kestrels found dead were killed as a result of collisions with vehicles along the interstate, indicating that traffic was not a major source of mortality. 

If this program sounds interesting to you, click on the "Getting Started" link.