After a summer hiatus, Science On Tap resumes Wednesday, Sept. 3, and the topic is one of interest to many Northwoods residents -- eagles.
The speaker will be retired DNR wildlife biologist Ron Eckstein. He will present "The Bald Eagle: The Fall and Rise of a Northwoods Icon."
Eckstein will talk about how various agencies used science to protect the eagle population, which has seen a resurgence in the last few decades.
Eckstein will share some history of the eagle population, talk about the eagles themselves, the history of eagle management and current management before taking questions and comments from the audience.
One thing Eckstein notes is how eagles and people have learned to coexist in recent years.
"Many of our crowded lakes ... we have nests that are right in with houses, right over people. Thirty years ago, that wasn't heard of," Eckstein said.
And he would know.
"I started with the DNR as a wildlife biologist here in Rhinelander in 1974 and in 1976 I started with the eagle program that I was very interested in," Eckstein said.
Vilas, Oneida, Lincoln, Langlade and Forest counties were Eckstein's main area during those years.
Retirement hasn't kept him from staying involved in the state's eagle program. He's still out in the field every year, he said.
Eckstein recalled a banding project that started in 1974 -- just two years before he began working with eagles. It ran until 1989.
"We tried to put a Fish and Wildlife Service band on every baby eagle in the state and back in the '70s, that was easy. We only had to get to about 80 nests to band the young," Eckstein said.
"After the mid-'80s ... it was becoming hopeless because there were so many eagles it was impossible to do that."
The reasons behind the banding study were to determine things like life span, where eagles go in the winter and mortality rates. They learned the average age of an adult eagle is around 10 years old, but a few live into their early '30s.
Researchers also learned about travel habits.
"We learned that the adults, in winter, never leave Wisconsin," Eckstein said. "They stay right here. Many of them stay right up here. Some go down to like the Mississippi or the lower Wisconsin for a little bit in the coldest (part of) January, but they don't stay put.
"The young ones -- the immatures -- do move as far ... east as Kentucky onto some big reservoirs; as far west as Oklahoma on some big reservoirs."
These eagles return to the north to breed.
Starting in 1990, Eckstein was the statewide coordinator for ongoing work in the bald eagle program.
That includes nesting surveys, of course, where researchers can find themselves climbing trees and peering into the nests to band the young. Luckily, despite their fierce look, eagles are not especially aggressive.
"They fly, they call, they circle, but they don't attack," Eckstein said.
For some raptors, it's a different story.
"An osprey -- they've been known to attack and hit. Ospreys are more aggressive. If you were banding in a great horned owl nest, they will attack. They'll hit you time and time again."
Goshawks are also quite aggressive when humans are in their nest.
Even red-winged blackbirds can be aggressive if a researcher is down in the cattails at a nest.
"They'll come and peck on your head," Eckstein said. Protective gear is employed.
Occasionally, an eagle will grab on.
Eckstein noted one windy day when he was climbing a tree to band eagle chicks. With the wind as cover, the adult eagle didn't hear the activity and was still in the nest when Eckstein reached it. The bird was facing away, feeding its young, and Eckstein figured he could get a band on the adult as well.
"I grabbed the eagle, but the eagle grabbed me," he said. "The young ones are one thing, they can kind of hurt, but they're not very strong ... but the adults are really strong. So, that's the worst I had ... getting into the nest with this eagle on my arm and then getting it off."
Researchers learn how to handle eagles, so even injured ones in the field seldom pose much of a risk. Eckstein said various wildlife rehab centers now recover many of the injured eagles.
Eagles have had to make a comeback, and plenty of human help was needed. Of course, it was humans that caused the need for a comeback in the first place.
Prior to European settlement, eagles were present in Wisconsin anywhere there were fish to eat.
During the earliest settlement in the 19th century, there were no laws protecting eagles.
"Eagles were indiscriminately shot, their nest trees cut down, cleared for agriculture or housing -- no concern," Eckstein said.
Eagles retreated to the Northwoods, but the Northwoods was soon cut over and large wildfires were common. It was tough for the eagles, but they maintained a presence in the north -- well away from people.
Then, during the World War II era, organochlorine pesticides were developed.
"It was a whole group of pesticides that included DDT (dichlorodiphenyltrichloroethane) and a whole group of similar ones," Eckstein said. "And these pesticides were really good at killing insects, but they ... halfway broke down and washed into lakes and rivers and contaminated lakes and rivers, got into tiny organisms, moved up the food chain. So, then fish, in their fatty tissue, had accumulations of the DDT breakdown."
Eagles ate these contaminated fish, and once the pesticide got into the eagles, they laid thin-shelled eggs which didn't hatch. Starting in the late 1940s, and into the 50s and 60s, the eagle population went into a decline.
Wisconsin led the way in getting the pesticides banned. UW scientists showed the relationship between the application of organochlorines and thin-shelled eagle eggs.
"Finally the state legislature, in 1969, agreed and banned the use of organochlorine pesticides in Wisconsin," Eckstein said. "Some other states did a few years later, then the federal government banned the use of that particular group of pesticides and they've been banned ever since."
By the late 1970s, the eagle population was beginning to rebound. Eckstein said inland lakes "cleaned up quickly."
The Great Lakes stayed contaminated much longer, especially Lake Michigan, which was slower to see eagles return. Eagles have started to nest and raise young on Lake Michigan in the last dozen years or so.
"Today, there's no place in Wisconsin where chemicals in the environment ... are causing any reproductive problems with eagles," Eckstein said.
Mercury and PCBs can be found in eagles, but not in levels that will cause reproductive harm.
"The biggest concern today is lead ... in the environment," Eckstein said. "Fifteen to 20 percent of eagles that are found dead have elevated lead levels now.
"It would be a good thing if hunters and fishermen would be OK with replacing lead sinkers and lead baits and lead shot and bullets with alternative metals. I think that would be a good thing."
Science on Tap is a partnership of the UW-Madison's Trout Lake Station and Kemp Natural Resources Station, together with the Lakeland Badger Chapter of the Wisconsin Alumni Association, the Minocqua Public Library and the Minocqua Brewing Company.
Science on Tap is held the first Wednesday of each month at 6:30 p.m. For more information, visit www.scienceontapminocqua.org.
Craig Turk may be reached at email@example.com
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