Kestrel Conservation

June 28, 2024

By Daniel Barringer, Preserve Manager and Claudia Winters, Natural Lands Assistant Manager

Claudia Winters, Assistant Manager for Sadsbury Woods, Willisbrook, and Green Hills Preserves, recently earned State and Federal permits for banding Kestrels and has taken on the role of coordinating Kestrel nesting boxes and conservation efforts on Natural Lands preserves and others in Pennsylvania. This complements the work that Steve Eisenhauer, Natural Lands’ New Jersey Regional Director, has been doing the last few years to promote Kestrel conservation through establishing and monitoring Kestrel nest boxes.

Claudia tracks the installation of Kestrel nest boxes and guides staff who perform the biweekly monitoring of eggs and nestlings so that we know how many hatched and when is the time window to band them.

The nesting boxes are mounted on long posts that are lowered to the ground on hinges just twice a year: once in the winter to clean them out for the next spring’s nesting season, and again just once to band chicks. This box and the hinged design was built by Force of Nature volunteer (and now Preserve Manager of French & Pickering Creeks Conservation Trust’s preserves) Jim Moffett. The dual-hinge design means that the box remains upright. Other monitoring of the eggs and chicks’ growth is done by attaching a cell phone camera to a long pole for a quick peak inside the hole, so there is minimal disturbance of the chicks and parents. See the earlier weblog post about how we do that. And here we are in the photo below, lowering the box in preparation for Claudia to band the Kestrel chicks.

People lowering a hinged post of a Kestrel nesting box

Photo: Molly Smyrl

American Kestrels are North America’s smallest falcon. Kestrels lay average clutches of 4-6 eggs.
Incubation is done by both the male and female and normally takes about 30 days. Kestrel nestlings fledge at about 30 days as well. Banding kestrel nestlings is generally between 14-25 days of age to be able to safely band them, determine sex and to ensure they are banded before they are ready to fledge.

Note that all banding, marking, and sampling is being conducted under a Federally authorized bird banding permit issued by the U.S. Geological Survey—the regulating agency.

Female kestrel chick in professional bird bander's grip

Photo: Molly Smyrl

Banding birds is like giving them an individual social security number and is a useful tool in the management and conservation of birds. Scientific information collected from birds, includes migration and dispersal patterns, breeding success, life span, survival rates, population growth and more.

Kestrels are sexually dimorphic, with females being slightly larger and less colorful than their male counterparts. One can start to tell sex around 14 days of age, with the primary feathers starting to emerge from sheaths and beginning to show brown and black barring in females, and bule-grey and black barring in males. They are still largely covered in down. These photos are of a female Kestrel, 22 days old.

Female Kestrel chick photographed after being professionally banded

Photo: Daniel Barringer

The differences between males and females will only grow over the course of their development. Around 25 days, females have barring on the breast and are primarily brown and black barred on the rest of the body. Males have a distinct rufous patch on the crown, rufous-brown body feathers, spotting on the breast, and blue-grey and black barring on the wings. The tail has a white terminal line, thick black band on the midline and rufous at the base. By this time many of the downy feathers are replaced.

A certified bird bander with a Kestrel nest box.

Photo: Daniel Barringer

After being weighed, aged, and banded, the Kestrels are carefully returned to the next box. Banding must be done early enough in their development that they aren’t so close to fledging that they might do so prematurely and therefore be subject to additional risk outside the nest box.

Kestrels are listed in Pennsylvania’s Wildlife Action Plan as a Species of Greatest Conservation Concern. Their population is in decline across the Northeast due to habitat loss, pesticides and inability to excavate their own nests. They rely on other species, such as woodpeckers, to make cavities and often must fight for the cavities with other cavity nesting species. Loss of habitat means less cavities available for nesting.

We are hoping that the establishment and monitoring of Kestrel boxes and populations on Natural Lands preserves will increase the numbers of this species of concern.