MIKE MILLER

This year marks the 35th year that I have had the opportunity to be involved with annual winter Bald Eagle counts along the Illinois River. Surveys provide a snapshot of Bald Eagle numbers on a particular day across the state. It is a “sprint” for the hundreds of people trying to get this picture across the state in a day. A single day of surveys does not tell us much about the population dynamics and long-term trends of Bald Eagle populations. Close to 60 years of eagle surveys in Illinois provide the “marathon” view of Bald Eagle population trends. Luckily, the trends seem to be positive for the Bald Eagle.

In winter, Illinois sees an influx of eagles that migrate from the north where ice cover keeps lakes and rivers frozen solid for months. They only migrate as far as they must in order to find open water and fish. This winter influx of Bald Eagles will return north once lakes and rivers in the northern U.S. and Canada open in the spring. We are experiencing a new trend in Bald Eagle population dynamics along the Illinois River: The increase of nesting pairs. When I started my involvement with eagle counts in the late 1980s, there was only one nest visible along my count route. Now, there are more than a dozen active nests visible in that same segment of the Illinois River. Our nesting Bald Eagles will likely not migrate away in winter. In fact, the adults will stay on their nesting territories year-round if there is open water. This has somewhat changed the winter population dynamics of Bald Eagle populations on the Illinois River. Since there is an increase in nests, there is an increase in territorial behavior of Bald Eagles in winter. Migratory eagles tend to not be as territorial since they are not defending their nesting site and are more tolerant of each other and cluster together in groups. The result is that an increase in territorial nesting pairs leaves less room for migrants to gather. Biologists call this “population dynamics.”

Trends in Bald Eagle population are closely linked to human actions. It wasn’t long ago that Bald Eagles were on the brink of extinction. It was not just one factor that led to their near extinction, rather, it was a perfect storm of accumulating circumstances. In 1782, the Bald Eagle became the national symbol of our fledgling country. At that time, there were more than 100,000 eagle nests east of the Mississippi River (the US was much smaller then). In the 19th and early 20th century, Eagles and many birds of prey were seen as vermin. Shooting birds of prey was not uncommon, especially on the river where there was an important fishing industry. While laws such as the Lacey act of 1900 protected the Bald Eagle, enforcement was lax at best. Also, during this time, expansive logging of river-bottom forests, and construction of levees, removed large trees and habitat needed for Bald Eagle nesting sites. Things got so bad for the Bald Eagle, that Illinois lost its entire nesting population by 1918. However, in 1940, the Bald Eagle Protection Act was established to further protect eagles. Part of that act outlined steps that needed to take place in order to improve eagle populations. In our region of the upper Midwest, an emphasis was placed on floodplain forest recovery. This allowed funding to be put towards purchase of habitat and incentivized the reduction of development in flood prone areas along major rivers. This represents our first steps on a marathon to improve nesting habitat for Bald Eagles.

In 1963, the Bald Eagle population in the lower 48 states was down to 417 nesting pairs. That same year, the Endangered Species Preservation Act listed the Bald Eagle as an Endangered Species. During this time, we also became aware that pesticides we were using were having unintended effects on the environment. DDT was a heavily used insecticide which accumulates in the food chain. The toxic effect caused the eggshells of birds to become so thin, that they would break during incubation. In 1962, Rachel Carson wrote the book, “Silent Spring,” which brought to the public eye the perils of toxins and how they are affecting birds. By 1972, DDT use was banned, and the Clean Air Act and Clean Water Act were poised to improve things. We were cleaning up our act. In 1973, one nesting pair had taken up residence in the state. A major milestone in our journey.

A pair of Bald Eagles on nesting territory at Spring Lake State Fish and Wildlife Area as seen through the spotting scope on Jan. 7.
Photo by MIKE MILLER

With decades of habitat improvement, reduction of toxic pesticides, improving water quality, and stronger protections, Bald Eagle populations began a miraculous recovery. Surveys in 1995 showed that the populations had reached a point where they were downgraded from “Endangered” to “Threatened.” By 2007, there were more than 10,000 nesting pairs in the lower 48 states and the population had stabilized enough to take them off the Endangered and Threatened species list. Data from 2021 Eagle Surveys estimate that there are more than 71,400 nesting pairs of Bald Eagles in the lower 48 states. The recovery of the Bald Eagle population is a success story to learn from.

Interpreting population trends of any species requires a “marathon” view. It is not a “sprint.” This roller-coaster mirrors the worst and the best reactions of the human species and measures our ability to reverse our deleterious impacts on the planet. Human ignorance, animosity, and greed forced Bald Eagles down a road towards extinction. Human enlightenment, empathy, and wisdom helped bring them back. In Bald Eagles, we can see our better angels, touchstones to the worth of our souls. Do we have the wisdom to apply what we have learned from the Bald Eagle towards other environmental challenges we increasingly face today? Time will tell. Just remember “population dynamics” are at play in all species, including our own. Let’s not sprint down a road of no return for the human species.