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Establishing a Nest Box Program for American Kestrels Along an Interstate Highway

Establishing Your Interstate Highway Nest Box Program for American Kestrels


The ideas presented here focus on providing kestrel nesting sites along interstate highways; they are applicable to any highways with grassy rights-of-way and road signs supported by steel posts.

The first step: Obtain permission from your local transportation authority to establish and monitor a nest box route.


Erecting Nest Boxes and Working Along the Interstate:

Building Nest Boxes

These may be built from any of the designs available. The design shown on pages four and seven provides enough board above and below the box for wrapping the banding material to secure the box to the sign-post. The kestrel nest box featured here is suitable for use in other locations, such as the outer wall of a barn or a windmill. We recommend white pine (#2) for box construction. Painting the boxes will increase their useful life. Using earth-tone paint (avocado, tan, or gray) allows boxes to blend in with the environment.

Safety Equipment

Abide by the guidelines set forth by your transportation authority. Use extreme caution while working along the interstate. It is advisable to have a yellow caution light on top of your vehicle and to wear a blaze orange vest and a hard hat.

Placement of Nest Boxes

Attach the box to the sign-post 10 to 30 feet above ground. Space the boxes, on average, one mile from each other and no closer together than one-half mile.

Box use by kestrels will most likely be highest in open areas where natural cavities are lacking. 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.

If a wetland is adjacent to the highway, using somewhat larger Wood Duck nest boxes will provide nesting opportunities for these birds as well as kestrels. Kestrels will use the larger Wood Duck nest box, but kestrel nest boxes are too small for Wood Ducks. Nest box plans for Wood Ducks are widely available. (see Nest Structures for Ducks and Geese).

Attachment of Nest Boxes

Metal banding material is used to secure the nest box to the steel sign-post. 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.

GIF - American Kestrel nest box
American Kestrel
nest box.

Checking and Maintaining Nest Boxes:

Nest boxes should be visited at least three or four times each year. The first visit should occur before the kestrels begin territory establishment. The date of the first visit will, of course, vary from one region to another. Because kestrels establish their territories in mid-March in Central Iowa, in this area the first box check is made in late February or early March. At this time, nest boxes are cleaned and repaired, and three to four inches of wood chips, wood shavings, or straw are added to the bottom of each box.

To monitor nest box use by kestrels, boxes should be visited two to three times during the nesting season. Several additional visits will be necessary to obtain accurate data to evaluate nesting success. To determine whether the young kestrels have successfully left a nest box, one visit should occur within five days of their expected nest departure. Because kestrels are especially sensitive to disturbance during the first two weeks of their 30-day incubation period, avoid visiting the boxes at this time (last two weeks of April in Central Iowa). The last visit should be made in late summer after nesting to remove old nesting material and to do repairs.

JPG - Young American Kestrel
Young American Kestrels hunting socially after nest departure.

European Starlings often nest in kestrel nest boxes. Starlings replace or cover wood chips with grass and other material and lay five, six or seven pale blue eggs. If starlings are found nesting, remove the nest and replace it with a new layer of wood chips. Sometimes kestrels will evict starlings from nest boxes. If this happens, the kestrels will use the starling's nesting material (see photo of kestrel incubating).

Records kept for each box on each visit will help to evaluate the sucess of individual nest boxes, the nesting sucess of your kestrel population, and ultimately, the sucess of your nest box program.

Previous Section -- The American Kestrel: North America's Smallest Falcon
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