Eagle numbers soaring
Eagles are soaring in Wisconsin.
The number of occupied eagles nests reached an all-time high this spring when a team of aerial observers from the Department of Natural Resources counted 1,504 nests across Wisconsin.
The nests were found in all corners of the state, although three counties — Milwaukee, Kenosha and Walworth — did not produce any evidence of breeding eagles.
There were four nests identified in Waukesha County, two nests each in Ozaukee and Racine counties and one in Washington County.
(Eagles, however, have occasionally been spotted in recent years in metropolitan Milwaukee.)
Statewide, osprey nests also were found in record numbers this year.
The surveillance took place in late March and early April with a DNR pilot and at least one other trained observer, as planes swoop within 100 feet of potential nesting sites for tale-tell signs of adults incubating eggs, said Jim Woodford, a DNR wildlife biologist stationed in Rhinelander.
With deciduous trees then leafless, "it's the best opportunity to see them and determine whether the nest is active," Woodford said.
The results are the latest sign of a comeback after eagles and other raptor species teetered on the brink of extinction in the 1960s and 1970s. Their renaissance was aided by a pesticide ban and protections in state and federal laws.
The number of eagles nests this year climbed from 1,465 to 1,504 — an increase of 2.7%. The number has been above 1,000 since 2005, according to the agency.
By comparison, in the first year of the survey in 1973, occupied bald eagles nests totaled 108.
Occupied osprey nests were up from 542 in 2014 to 558 in 2016. An osprey survey was not conducted last year, according to the DNR, as an experiment to see whether fewer observations — a cost-saving measure — would still provide helpful information on the birds.
Milwaukee County did attract one osprey nest. Three osprey nests each were found in Waukesha and Washington counties, one each in Ozaukee and Racine counties and none in Kenosha County.
Woodford said the agency thinks that eagles will eventually start nests across the state — even Milwaukee County, where viable sites can be found along the Milwaukee River and Lake Michigan.
The birds' comeback can be attributed to several factors.
The federal Bald and Golden Eagle Protection Act makes it illegal to kill or possess an eagle. In Wisconsin, the bald eagle was removed from the state endangered list in 1997 and taken off the federal list in 2007. Many protections are still in force, however.
Pollution control laws have helped improve water quality, meaning fish that are eaten by eagles are consuming fewer pollutants.
The pesticide DDT was banned in 1973. The chemical thinned eggshells, which had a devastating effect on reproduction.
And then there are the birds themselves and their adaptability. "These birds have shown that they are very adaptable," Woodford said. "All they need is a little pocket of habitat."