American Kestrel - Photo Mick Thompson

The human side of the American Kestrel’s 2021 nesting season involved thirteen trips where Dick Phillips drove more than twenty miles from his home in eastern Delaware County to my home in Delaware, Ohio. Then, after we loaded my fiberglass extension ladder and other materials into Dick’s truck, we traveled more than fifty miles along country roads to check on eighteen kestrel boxes that hang from utility poles. All boxes are more than one-half mile  from other kestrel boxes so we can practice what has been published about our continent’s smallest falcon’s nesting territories and their intolerance toward their own species during nesting seasons.

Our annual monitoring began on March 16 and we ended up adding white pine bedding to seven boxes that most likely had been excavated by European Starlings. We counted 16 kestrels outside the boxes as they flushed from, or remained on, utility wires near their future nest sites.

Only once during our first monitoring trip was a kestrel concerned by me being on a ladder more than twelve feet above the ground and peering into Box-9. The female kestrel swooped several times after I had opened the box’s hinged roof to peer into the nest cavity. A question quickly came to my mind; was this the same female that hit me in the head the previous year as I checked Box-7 that happens to be only 0.8 mile north of Box-9? Switching boxes between nesting seasons is common among kestrels.

I usually give names to aggressive birds that I encounter on my nestbox trails. I’ve written about “Macho Man,” an aggressive male bluebird, and “My Little Chickadee” that would scold me from several feet away every time I checked her nest, and several female Tree Swallows that I had captured multiple times when I was studying nesting swallows that I had banded. I did not formally name the two, but I just recognized them when I felt the air currents from their close dives. 

So, do I have a name for whom I think is a swooping kestrel that continues to protect two nestboxes during separate seasons? Yes, recently, I decided to call her “Swooper.” At first, I thought “Swoopie” would be good, but then, Swoopie doesn’t sound strongly enough to adequately describe her personality. She has earned a strong name. I enjoy aggressive birds as they give me unforgettable interactions.

Kestrel Nestbox with Two Eggs Hatched
On April 26, 2021, two of Swooper’s eggs had hatched and all five hatched and grew to fledge.

On our second monitoring trip that took place on April 10, fourteen kestrel nests were active with eggs. Kestrels lay one egg every-other-day and the female starts incubation after the next-to-last egg is laid. Most interesting on April 10, was that adult kestrels were on nine of the nests; females were on eight nests, and a male was on one. Our adult kestrels seem to accept us lifting nestbox lids to peer into their world. We have never tried to capture the adults for any reason, simply because we do not want to bleed.

I try not to criticize other projects, but I will admit that I can’t picture myself opening a side-opening nestbox to peer face-to-face with an adult kestrel. I think it might be too dangerous for my eyes and face.

Sixteen days later, on April 26, we counted fifteen active nests with eggs and Swooper’s nest had eggs that were hatching. The aggressive mother was not near her nest, so no adrenalin flowed.

Male Kestrel in Nesbox
On April 15, 2012, a male kestrel was photographed as he was giving his mate a break.

Two European Starling nests were recorded and five eggs were removed from one. The starling nests were allowed to stay in their boxes since kestrels will reshape a starling’s round nest cup into an elliptical one, usually after consuming the original owner.

One additional box had an elliptical shaped kestrel cup in its white pine bedding but the box failed to become active with kestrel eggs. 

Fifteen days later, on May 11, nine adults were on their nests and eight nests had visible nestlings and a leg banding expedition was planned. We aim to band nestlings between fourteen and twenty-four days old. You can sex kestrel nestlings at twelve days due to the coloration of emerging wing and tail feathers. Since most nests will have one nestling that is several days younger than its siblings, we wait until a family will be two weeks old before banding. There was no need to waste time.

We checked fourteen nests on May 19 and ended up banding 27 nestlings from six families. We returned to band 19 from four families on May 26, and banded the last five falcon families of twenty-five young on June 2.

Since the record latest first egg date for our kestrels is June 25, we wait until days after the July 4 holiday to check the boxes to make sure we don’t miss a late nest. This year there were three eggs representing a second brood in Box-4. A second check on July 31 found three nestlings with faint feather sheaths that indicated their ages to be eight days or older according to photos in American Kestrel Nestlings, a 36-page booklet published and distributed by Zip Publishing in Columbus, Ohio.

Unfortunately, when we arrived on August 7 to band fifteen-day-old nestlings, both parents flushed from the utility wires but only two of the three nestlings were in the nest and they were dead, having died several days earlier. As Dick dropped the remains from their nest, I salvaged the best specimen for presentation to one of two university museums. Hopefully, it will “live on” as a study skin.

Only one task remained, and that was to clean out used nests from the project’s 18 boxes and add new white pine bedding. Cleaning a kestrel box begins by lining the ladder up with the pole so the ladder will also be lined up with the box’s side. After the ladder is extended to its maximum length, a nylon strap is used to tie the ladder to the pole below the box.

I like to wear a carpenter’s apron that holds a garden trowel and a putty knife. I slide the handle of a spackle knife in my back pant’s pocket. The spackle knife’s blade is six inches wide and is used to slice between the caked nest and the side of the box. The top layer of a used kestrel nest is caked excrement that glues the bedding into a dry solid layer up to one-inch thick.

To dig out an old kestrel nest, you must climb high enough so your entire arm can enter the nest cavity. The trowel is used to break and pry the layer away from the box’s side surface. Once the used nest layer is broken, you use your hand to crush the pieces to feel for bones of possible prey items or nestlings that did not make it.

Also, once nest fragments are dropped over the box edge, they can be stomped to reveal past histories. Your second hand and arm are used to hug the utility pole for stability.

No kestrel remains were found this year, not even in the failed nest in Box-4.

On October 9, we cleaned and added new bedding to all eleven boxes along country roads east of State Rt.23, and four days later, we cleaned and updated the seven boxes west of Rt.23. As expected, cicada wings were found in many of the boxes. During banding events, all nestlings were found to be healthy, and a year of 71 fledglings is quite impressive.


American Kestrel in flight – Photo David Zieg

The project’s kestrels had a fantastic season. Kestrels attempted 16 nests and 15 (93.8%) successfully fledged young. Seventy-seven eggs were laid, 75 (97.4%) hatched, and 71 (92.2%) fledged. After hatching, 94.7% of the hatchlings grew to fly from their nests to start adult lives. Among the successful nests, the average fledged per nest was 4.73.

The best statistic is that 1,359 young falcons have been raised since the Delaware County American Kestrel Project’s first  successful nest in 1995. If you are reading this, and you were a student in one of the county’s schools where you recycled and sold aluminum cans to financially support the first ten nestboxes, be proud that you helped to launch a very successful project.

Conserve on for our smallest falcons!