With winter temperatures dipping below freezing, the Illinois River takes on a whole new personality. At this year’s Eagle Day at Forest Park Nature Center, the sub-zero wind chills kept the human population low. But the hardy folks who came and joined us on the shore of the Illinois River were greeted with the view of over a half-dozen bald eagles. With the river fully frozen, most were sitting on the ice near the barge channel waiting for something to show itself in the small openings in the ice. It’s a hard way to live, but the bald eagle has survived greater hardships.

This year marks the 55^th time that the Eagle Nature Foundation (ENF) has conducted its annual Midwinter Bald Eagle Count. The U.S. Geological Survey (USGS) also conducts a nationwide count in Mid January. Both of these counts help us better understand eagle populations. The local Peoria Audubon Society has been involved with the ENF count since the mid 1960s, when Bert Princen helped organize teams to count eagles from Henry south to Havana. A glance at the data shows positive trends in this stretch of the river. Eagle numbers have grown since the early days of the count, and the recovery of the bald eagle is a great example of how a species can be brought back from the brink of extinction.

To understand the population trends, we need to first understand why eagles were almost lost. There wasn’t just one factor that lead to near extinction, rather it was a perfect storm of events that lead to their near demise. In the 19^th and early 20^th centuries, 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, heavy logging of river-bottom forests removed large trees needed for nesting sites. A final insult was the use of toxins that accumulate in the food chain. DDT was a heavily used insecticide that caused the eggshells of affected birds to become so thin, that they would break during incubation.

Things got so bad for the bald eagle, that Illinois almost lost its entire nesting population. In 1973, only one nesting pair was known in the state. Winter populations were not much better. In winter, Illinois sees an influx of eagles that migrate from the north where ice cover keeps lakes and rivers frozen solid for months. Eagles only migrate as far as they have to in order to find open water. When Peoria Audubon started midwinter counts in the mid 1960s, fewer than 75 eagles were found on the stretch from Henry, south to Havana. Today, it is not unusual to see over 300 on that same stretch of river in January. Nesting eagles in Illinois have also increased. Now, there are over 130 nesting pairs in Illinois. The story behind their return from the brink of extinction is a true success story.

In 1940, the Bald Eagle Recovery Act was enacted 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 toward purchase of habitat. This, combined with an effort to reduce development in flood prone areas along major rivers, created the stage for increasing available nesting habitat for bald eagles.

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. By the 1990s many floodplain forests had reached an age and size that they could support eagle nests again. By the turn of the 21^st century, eagles were making a comeback.

While bald eagle recovery is a success story, keeping track of trends is important, and threats still exist. USGS midwinter surveys show a decline in eagle numbers on the Illinois River north of Peoria. ENF surveys show a decline in the ratios of immature to adult eagles. Now isn’t the time to take our finger off of the pulse of the patient. There is still work to be done.

To learn more about the Midwinter Bald Eagle Counts, results, and how you can help, come to the Peoria Audubon Society’s Feb. 11 meeting, 7 p.m. at Forest Park Nature Center in Peoria Heights.