Thirty years ago, eagles were a rare site.
But it’s hard to pass a waterway these days without seeing one glide aloft or perched high up on a branch.
So it might seem strange that eagle experts who came to Rochester from the Eagle Nature Foundation over the weekend worry the eagle population might not be as secure as it appears.
They worry about lead and its potential effect on eaglets. Also, they worry about wind power and potential disruption to nesting sites.
What harm will it do the overall eagle population if but one eagle dies when it strikes the blade of a wind turbine?
If that happens 10,000 times at wind-power sites across the country, said Mark Shieldcastle, research director of the Black Swan Bird Observatory in northern Ohio, the effect becomes significant.
Shieldcastle said in an interview that Minnesota eagle enthusiasts worry they do not have enough of a voice in finding ways to bring wind energy while at the same time protecting established eagle nesting sites.
Wind power should get established in locations where there are no established nests, Shieldcastle said.
The eagle population largely has recovered from the Silent Spring days, when eaglets died so commonly the national symbol became rare. Under rules that protected them, the eagles rebounded and now can be seen in large numbers along the Mississippi River and even along southeast Minnesota’s Zumbro River.
“Wind power is bringing new rules that have not been evaluated,” Shieldcastle said, suggesting the effect of wind power on eagle numbers remains unclear.
Iowa researcher Billy Rieter said his group has been studying how much lead is present in eagle droppings and trying to figure out if there should be worry about eaglet survival.
Their study showed eagles eat all different types of birds, mammals and even a surprising number of turtles, playing a role at the top of the food chain.
Under federal guidelines, Shieldcastle said, a site close to an eagle nest is supposed to be abandoned as a possibility for a wind turbine.
It’s not clear, he said, whether eagles have reached a “threshold level” of being able to survive despite habitat disruption. But the cost of recovery if a plummet in eagle numbers isn’t recognized in time would be “immense.”
It takes time to notice a drop in numbers, Shieldcastle said. It might be 10 years before it’s clear the eagle population is dwindling and another 10 years to get a restoration project under way. By that time, recovery would be much more difficult.
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