by Kristofor Hustedand Leslie Trew Magraw, Medill Reports, news.medill.northwestern.edu 10 March 2011
The eagles have landed … in Illinois.
Volunteers counted more than 2,100 bald eagles in the state for the midwinter 2011 survey. The numbers of adults and juveniles recorded for the iconic species have reflected a consistent and healthy breeding population, according to Jo Skoglund of the Illinois Audubon Society.
The Illinois Audubon Society took over bird-monitoring duties from the Illinois Department of Natural Resources in 2006 as the birds were in the process of being removed from the federal list of threatened and endangered species.
Between Dec. 31 and Jan. 9, groups of volunteers hiked out for a day to 45 historical survey sights along the Illinois and Mississippi rivers and used scopes and binoculars to count the immature and mature bald eagles they encountered.
Characterized by their dark feathers and beaks, immature bald eagles are generally fewer than five years old and not yet able to breed. These young birds made up 37 percent of the eagles counted this winter. As bald eagles mature, their head and tail feathers turn white and their beaks turn yellow. Birds that fell into this category comprised the remaining 60 percent of the total tally. Volunteers weren’t able to categorize the remaining 3 percent.
Experts differentiate between maturity levels to keep an eye on the breeding health of the species. Since 1992, the ratio between mature and immature eagles has held relatively steady.
The organization has kept the survey sites consistent with the historical routes despite eagles showing up in places outside of these areas, according to volunteer coordinator Skoglund.
“Now we have so many eagles all over the state,” she said. “We’ve got eagles at Starved Rock, Geneva and the suburbs of Chicago but it doesn’t make much sense to add routes [to the study] because it will just skew your numbers.”
Last winter, only about 1,200 birds were counted – but according to Skoglund, this is no cause for worry. Because the organization sets a relatively narrow window for the survey to be completed, storms can have a big impact on the results. Last year was one of those years.
“The river was way up and it was frozen which means the eagles took off to other parts,” she said. “And there were parts of the route that [the volunteer surveyors] couldn’t even get to because the conditions were so treacherous.”
This year, Skoglund and her counting partner had to cut their time short in the early afternoon because the snow began to fall and decreased visibility to nearly zero.
“You have to look at these numbers as a trend,” she said, “because to look at 2011 and say ‘Wow, we got twice as many eagles as last year’—well, we saw twice as many. That doesn’t mean there are twice as many.”
Many of the volunteers have been participating in the national bird count for years. And just as they keep returning for the avian census, the bald eagles do, too.
How the national bird is faring in the rest of the nation
Long-touted as an endangered species success story, our national bird still encounters many threats. In addition to habitat loss and industrial contaminants, bald eagles could be facing a new danger from an unlikely source: wind turbines.
Though bald eagles are doing well in Illinois and the Midwest in general, they could be at a heightened risk from the growing prevalence of wind energy projects – particularly in California and the rest of the American West, a boom region for industrial-grade wind facilities.
The U.S. Fish and Wildlife Service recently issued a draft conservation plan to help wind developers reduce the risk of eagle collisions at wind facilities. A nationwide public comment period was opened on the Draft Eagle Conservation Plan on Feb. 18.
The guidelines will also help developers comply with the Bald and Golden Eagle Protection Act, the principal legislation safeguarding bald eagles since they were removed from the list of threatened and endangered species in 2007. The birds are also protected under the Migratory Bird Treaty Act.
According to Matthew Sailor, a U.S. Fish and Wildlife Service bald eagle coordinator and a member of the team that drafted the wind conservation guidelines, bald eagles are less likely to be killed by wind turbines than golden eagles. Because bald eagles don’t typically forage for food around wind towers, as golden eagles are known to do, they are more apt to have their eyes off the ground and alert to what’s going on around them.
Sailor said the location of the turbines themselves could also help explain why mortality rates aren’t higher in the state.
“It’s not as pressing of an issue here [than it is in the West], mainly because we see our wind developments in areas that are much more devoid of eagle habitat,” he said. “You see them in central or northern Illinois – and, typically, our eagles are along the major waterways.”
Sailor, who oversees bald eagle conservation efforts for the Fish and Wildlife Service in Illinois, Iowa and Missouri, said the agency recommends that wind developers stay 10 miles away from rivers – and so far, most of them have complied.
While Douglas Stotz, a conservation ornithologist at the Field Museum, considers bald eagle comeback a success story, he cautioned that “at the same time, it’s sort of fragile.”
“Although they’ve increased dramatically in Illinois, the number of breeding pairs is not huge,” he said.
Bald eagles and other birds of prey were on the brink of collapse in the lower 48 States starting in the 1950s, largely the result of exposure to DDT, a once ubiquitous crop dusting pesticide that thinned their eggshells and led to extremely low breeding success.
Though that pesticide was banned in 1972, leading to the bald eagle’s eventual resurgence, Stotz said other industrial contaminants pose serious threats to eagles and other large predatory birds.
He said polychlorinated biphenyl – a chemical that and commonly referred to as PCB – poses a particular danger. He said the industrial contaminant gets into the water and then the fish eat it. “It’s basically the same thing that happened with DDT,” he said. “It increases as you move up the food chain. And because eagles are at the top of the food chain, they get the biggest dose.”
Even though PCBs were banned in the U.S. in 1976, not long after DDT itself was banned, they remain in the environment much longer than DDT and are still present in many appliances. Much of the Great Lakes area is still heavily polluted with PCBs, despite extensive remediation work.
Stotz said that after being metabolized to a certain degree, PCBs work as feminizing agents.
“You have some examples where there’s large concentrations of large, fish-eating birds where the males aren’t actually male – they’re sterile or they have both male and female reproductive organs.” Because PCBs are very long-lived, “what we put out there tends to hang around,” he said.
According to Sailor, persecution – whether it’s hunting, trapping or poisoning – is still a major cause of mortality for bald eagles. “There are just some people who don’t care about birds,” Sailor said. “I don’t know if they think it’s fun or cool or what.”
Because eagles are opportunistic eaters and often feed on carrion, they are also susceptible to being killed by cars and trucks on the highway.
The habitat protections afforded by the Endangered Species Act safeguarded the nesting, feeding and roosting sites that ultimately allowed the eagles to bounce back. But now that the species has been removed from federal protection, there are few restrictions on development in the areas that had been previously protected.
Sailor said that “habitat destruction and fragmentation is a big problem” for eagles and other species. “From a wildlife perspective, the most important issue is almost always habitat,” Stotz said. “Without the habitat, it wouldn’t matter that we got rid of DDT.”
Even though bald eagles face continuing threats like any other species, they have still made a remarkable recovery. And as our national bird, their dramatic story has drawn critical attention to the importance of wildlife conservation.
“Eagles are one thing that people definitely respond to,“ Stotz said. “The random kangaroo rat from somewhere in California just isn’t going to make that big of an impression with most people compared to the bald eagle.”
URL to article: https://www.wind-watch.org/news/2011/03/10/eagles-continue-steady-climb-despite-emerging-threats/