Placing, protecting and mounting your American kestrel nest box

Safety

The Iowa DOT's number one priority is safety.  Carefully read and abide by the guidelines set forth by your local transportation authority. 

Use extreme caution while working along any roadside, especially the busy interstate system.  It is advisable to have a yellow caution light on top of your vehicle and to wear a safety vest and hard hat. Orange safety vests are available for loan from the Iowa Department of Transportation’s maintenance facilities.

Children should never put up a kestrel nest box alone.  Make sure at least one adult is helping.  Contact a professional if you need assistance putting up the box.  Use a ladder and make sure someone holds the bottom.  Don’t work alone!

Placement of Nest Boxes

Proper placement of the nest box is important.  Place nest boxes between 10 to 30 feet above ground and mount on a signpost, pole or tree. The most common placement height ranges from 10 to 16 feet. It is important that you locate the nest box within easy reach by ladder for monitoring and cleaning. 

The opening should face a southerly to easterly direction.  The entrance should be unobstructed with a clear flight path.

Space the boxes, on average, one mile from each other and no closer together than one-quarter mile.  Nest boxes closer together than ¼ mile may cause fighting between males.  The distance between boxes is determined by the amount of suitable habitat.  Interstate roadways provide the widest right-of-way areas, allowing for boxes to be placed in closer proximity to each other.

Choose a site in an open area, rather than a heavily forested one.  A forest/field edge setting is also a good location  

When selecting your site, scout the area for perch sites.  Perch sites are an important habitat component due to the predominance of perch hunting by kestrels. Perch sites include trees, utility poles and lines, and fence posts.  There should be at least one perch site for every five-acre habitat area.

Box use by kestrels will most likely be highest in open areas where natural cavities are lacking. Don’t be discouraged if the birds do not begin nesting in your box immediately; sometimes it takes time for the birds to find it.  However, if a box has been in place for three or four years and has not been used, it is advisable to choose a new site.

In Iowa, kestrels may begin looking for suitable nesting sites toward the end of winter into early spring.  For this reason, it is important to have your kestrel box mounted by late February.

A few words of caution:  When scouting out a suitable habitat, avoid selecting an area where pesticides and herbicides are used.  These agents are not only harmful to birds, they decrease and sometimes eliminate inspect populations, the primary food source for the kestrels.

If a nest box is placed near a road, place the box so the entrance faces away from traffic.  This will prevent the fledglings from flying into the road when leaving the nest.

Protecting the box from predators and competitors

Although nesting boxes serve the wonderful purpose of providing nesting opportunities for many native birds, they can also provide easy targets for predators and unwanted competitors. Common predators of nest boxes include raccoons, snakes, cats, and squirrels. 

The most passive way to prevent predators is to avoid placing nest boxes in areas where predators are prevalent.  But, because some predators are prevalent everywhere, this is often easier said than done.  It is important not to place the pole or nest box close to wires that allow raccoons, cats, or squirrels to gain access to the nest box.

Metal predator baffle

Photo credit: Courtesy of Cornell Lab of Ornithology

Generally speaking, whether the nest box is mounted on a wooden pole or tree it will require the installation of a predator baffle.  For an effective and easy baffling method, tightly fasten a 2-foot wide piece of slick metal flashing around the pole or tree.  Place the flashing between 4 to 6 feet off the ground to prevent a predator from climbing the pole.  When locating a box near a roadway, the preference is to use a natural-colored metal flashing in a brown, crème or other neutral color.  Bright metal sheeting can cause a glare on sunny days, which might create a safety concern for motorists.

Conical metal collar

Photo credit:  Courtesy of Cornell Lab of Ornithology

Another type of guard is a conical metal collar.  This guard works well for boxes attached to free-standing poles.  The collar is a circular piece of galvanized sheet metal that is placed around the pole or underneath the nest box.  If a metal pole/post is used, flashing may still be necessary since raccoons often climb metal posts, too. 

 Attachment of Nest Boxes  

There are lots of ways to mount, or attach, the box.  If you are mounting to something wooden, large screws are best, but 16-penny aluminum/galvanized nails will work too.  Using double-headed framing nails is another option that makes withdrawal of the nails easy when relocation or replacement of the box is needed.

Be sure to pre-drill holes in the box backboard, so you don’t split it.  Use two screws or nails on the top and one or two on the bottom.  Make sure the box is secure and won’t wiggle.  Remember, if the box isn’t solidly secure, predators like raccoons might knock it loose, causing it to fall to the ground.   

Another option is to use a metal clip, as illustrated below.

Image credit: Printed with permission from Woodworking for Wildlife (Hassinger 1998)

If you’re mounting onto something metal, pre-drill two holes on the top and two holes on the bottom of the backboard.  Using bailing wire to wrap three to four times through your box holes and around the metal pole.  Make sure the bailing wire is tight, and no loose ends are sticking out that could harm an incoming kestrel.

Images credit: Printed with permission from Woodworking for Wildlife (Hassinger 1998)

If you wish to attach a box to a living tree, do not use nails or screws.  Rather, slip a strand of galvanized wire through the vent holes and attach a bungee cord to both ends.  Stretch the bungee cord around the tree, preferably over a limb.  Or string a galvanized wire through the vent holes, attach a rubber-coated wire (or hose with wire run through it) and loosely drape over the limb. Remember, however, that hanging boxes from trees provides an easy route for predators to reach the box.  (Note: While attaching a box to a living tree remains a viable option, it is the least desirable since predators such as raccoons and cats invariably have access to the nests.)

American kestrel nest box installed on back of interstate sign

Photo credit: Courtesy USGS, Northern Prairie Wildlife Resource Center

For mounting the nest box on one of the Iowa DOT’s steel sign posts metal banding material should be used. To install, use "C"-clamps to hold the box in place while working. Bands are applied with a tool that is normally used for strapping steel bands around freight. This steel binder is expensive, but is available for rent at many of the outlets that rent tools. One strap is wrapped around the sign-post and board extending above the box, and a second strap is wrapped below in the same manner (see photo). A third strap may be wrapped around the entire box and post and will help hold the box in place in high winds. Stainless steel banding is more expensive than galvanized steel but will not require replacement. In Iowa, galvanized steel banding rusts and breaks in about six years.  DOT maintenance crews may be able to assist you with the installation of your box if it is being mounted on the back side of an interstate road sign.

Whichever method you choose to erect your boxes, be sure your box is secure enough to withstand high winds and severe weather.  Above all, be safe.  Don’t take chances and never work alone.  Children must  have at least one adult helping.

Getting your box mounted is just the beginning.  Being a good landlord of your box is extremely important.  Boxes that are not maintained are likely to attract European starlings. An over abundance of this species can be harmful to Iowa's eco-system.   Click on the "Being a Good Landlord" button to learn more about your caretaking responsibilities