Can They Hack It? A Decade of Efforts to Re-Establish Osprey in Illinois

The osprey (Pandion haliaetus) was listed as a state-endangered species in Illinois in 1997. Similar to many of its fellow raptor cousins, osprey struggled to thrive following years of habitat loss and the degradation of waterways essential to their food source and nest site selection. Additionally, population declines were closely tied to the introduction of DDT after World War II, drastically increasing the prevalence of hatching failure. 

In 2012, Illinois Department of Natural Resources (IDNR) biologists Patrick McDonald and Joe Kath designed a program to give osprey a boost in building a self-sustaining breeding population in Illinois.

 “We received help from several individuals and organizations to get this project running,” said McDonald.

Along with McDonald and Kath, Dr. Tih-Fen Ting, a professor of environmental studies at the University of Illinois-Springfield, and other research-focused individuals worked to implement the plan in the summer of 2013. Using a translocation method known as hacking, osprey chicks are collected from healthy populations in other states and are transported to Illinois where they are placed into a “hack box.” The hack box serves as a makeshift nest for the chicks to grow and become familiar with their new surroundings, while also protecting them from dangerous weather and predation by other species until they are ready to fledge.

2023 marked a decade of translocation efforts, via hacking, in Illinois. Many neighboring midwestern states have reportedly had successful translocation projects through hacking. Similarly, Illinois can report that our project has seen its success.

A Decade of Work Leads to Breakthrough

Since the summer of 2013, Illinois’ osprey hacking project has collected 132 chicks, with 125 successfully fledging and 115 believed to have survived up through the time of migration. Hacking sites were located at Anderson Lake State Fish and Wildlife Area (SFWA), Banner Marsh SFWA and Lake Shelbyville State Wildlife Management Area (SWMA). Of those 115 chicks, 70 were males, 33 were females and 12 were of unknown sex.

You will note that the number of males released is significantly higher, which is correlated with trends in osprey nesting site fidelity. While nesting site fidelity, an animal’s tendency to return to the same location to nest year after year, is a common characteristic in birds, it is a more typical trait in females. For example, in wild turkeys (Meleagris gallopavo) and wood ducks (Aix sponsa), the high nesting fidelity of the females determines the location of the nest or cavity. In contrast, male osprey tend to be the most likely to return near the areas they fledge from. A decision was made a few years into the project to release all males, where possible, to increase the likelihood of individuals returning. This strategy appears to be working, as the individuals reported to have returned near their release sites have been males.

With the obvious emphasis on the likelihood of males returning, the project focused on affixing Platform Transmitting Terminal (PTT) tags to male chicks. Platform Transmitting Terminal (PTT) tags are used in satellite telemetry to send periodic location coordinates for the subjects under observation. Much like your Amazon order is assigned a unique tracking code that allows you to monitor the package’s movement, male osprey chicks affixed with PTT tags are monitored as they fledge and begin migration to Central and South America to, hopefully, monitor the route they take back to their nesting site.

 From 2014 to 2023, 23 male chicks were assigned PTT tags. Of those 23 chicks, six successfully fledged and migrated to Central/South America.

Transmissions from successfully fledged osprey are monitored to determine their location and likelihood of returning to nesting sites. In some cases, hacking procedures have proven successful and the bird’s PTT tag has confirmed its behavior and route upon returning.

26R is no Lame Duck

A male fledgling hacked at Banner Marsh SFWA, 26R, was tagged using PTT in 2022. After successfully fledgling, 26R began migrating south in September 2022. In mid-October 2022, 26R was confirmed to have made it to the Chame Bay Mangroves in Panama, where it stayed for the better part of a year, with most of its time spent exploring the sandy islands that are a popular spot for migrating shorebirds. Satellite technology confirmed that 26R continued to stay near the Bay, however, the bird had begun to expand its movements from January to March of 2024, likely preparing to begin the return trip for the nesting season.

In late April 2024, 26R began to migrate northward, where it reached the shore of Yucatan in early May. By mid-May, 26R had reached the Missouri-Iowa border. From then on, 26R roamed through parts of Missouri, Iowa and Illinois before finally finding its way back to Banner Marsh SFWA on May 30, 2024. During June 2024, the last month of the project’s yearly segment, 26R spent most of its time in the area of its release site, often exploring neighboring counties between its release site along the Illinois River and the Mississippi River.

A Hope-Filled Future for Osprey in Illinois

As of 2024, both current hacking locations, Banner Marsh SFWA and Lake Shelbyville SWMA, have confirmed the return of hacked males and their mates along with the occasional unbanded pair. While the return of hacked birds in Illinois is not a novel thing, with confirmed returns of hacked birds going back as far as 2019 at Lake Shelbyville, subsequent years have produced reports affirming even more hope for success as mated pairs now hatch chicks.

24D, a male hacked at Anderson Lake SFWA in 2015, along with his unbanded mate, returned to the area to build their nest atop a utility pole that was no longer active. Together they hatched two chicks with one of them believed to have successfully fledged. Additionally, on the top of a dead cottonwood tree not far from the hacking box at Banner Marsh SFWA, a pair of unbanded adults built their nest. Together, they produced two chicks in 2023 and 2024.

04R, a male hacked at Lake Shelbyville SWMA in 2020, and its mate returned to one of five nesting platforms. Together they produced two chicks in 2023 and again in 2024. While it has not been confirmed that their chicks successfully fledged, the family was monitored into late June 2024 when it was confirmed that both chicks were alive and appeared healthy.

Although the small number of returning birds out of the 125 released appears to show limited success of returning birds, the nesting of unbanded birds affirms that there is significant hope for reestablishing the osprey population in Illinois. In comparison to neighboring states which conducted similar hacking projects, Illinois is only halfway into the time and number of birds hacked to begin seeing a prominent return of birds.

“In the case of 24D, it was nine years from its release before we received a report of this bird’s return to Illinois, when it most likely has been coming to the same area for the past seven years,” said McDonald. “And this pair has likely produced offspring which have returned to breed, as well. I believe there could be several more individuals released during our project which may have returned that we are unaware of simply because they have not been observed or reported.”

Additionally, it seems that the average number of years before a mated pair successfully returned for nesting falls at roughly the five-year mark. Ospreys reach breeding age at 3 to 4 years, so there is a slight lag period when birds returning as adults begin to produce offspring. This means that, although slow to start, Illinois might now begin to see a much higher return of osprey.

Be sure to look up, you never know what might be flying overhead this coming spring.

---

Kaleigh Gabriel is a Wildlife Outreach Specialist with Lewis and Clark Community College, working out of the Illinois Department of Natural Resources building to assist the Division of Wildlife Resources. Growing up just between Sangamon and Christian counties, she spent a lot of her time hunting and fishing in Illinois. She received her bachelor’s degree in writing/journalism from Manchester University, Indiana.