Of bats and birds and the wind turbine in Lewes
It’s a pretty big story across the land. Wind turbines and birds and what happens when they meet.
Just last week, the U.S. Department of Justice announced the first-ever criminal conviction under the Migratory Bird Treaty Act for unlawful avian takings at wind projects. Duke Energy Renewables of Charlotte, N.C., pleaded guilty to violating the act in connection with the deaths of 163 protected birds over the course of the last four years. Of the dead birds found among the 176 turbines at two Wyoming wind farm installations, 14 were golden eagles.
A Department of Justice press release states: “Pursuant to a plea agreement with the government, the company was sentenced to pay fines, restitution and community service totaling $1 million and was placed on probation for five years, during which it must implement an environmental compliance plan aimed at preventing bird deaths ... .”
One of the big factors in the conviction was that Duke, despite prior warnings by the U.S. Fish and Wildlife Service, “failed to make all reasonable efforts to build the projects in a way that would avoid the risk of avian deaths by collision with turbine blades.” Nonetheless, Duke cooperated with the Fish and Wildlife Service investigation and has implemented measures aimed at minimizing avian deaths at the sites.
At the University of Delaware’s wind turbine site in Lewes, a two-year study on bird and bat impacts confirms certain problems. The clearest problem comes from researcher Jeff Buler’s findings that of nine confirmed bird kills and collisions at the Lewes turbine, three of them were ospreys. “There’s an abundance of ospreys in that area, nesting and migrating. They’re there every day, flying around the turbine. We don’t know that the ospreys killed were nesting birds, because it was during the migrating period.”
In the university’s Department of Entomology and Wildlife Ecology, Buler said moving nesting platforms away from the turbine is a likely recommendation coming out of the study.
He said the study projects that the Lewes turbine is probably killing about 14 birds per year. “That’s pretty inconsequential when you consider that our surveys detected about 35,000 total birds in close proximity to the turbine during the study period.”
Bat mortality much higher
Less obvious but probably more significant is the number of bats killed by the Lewes turbine. “Over the two-year period we found 68 bat carcasses near the turbine,” said Buler. “Most of them are adult, male, eastern red bats - a migrating tree bat.” Buler said the study, with corrections to the data, projects that 110 bats per year are killed by the turbine. The corrections account for things like carcasses carried away or eaten by scavengers before they’re found by researchers - or simply missed by those walking daily grid patterns beneath the turbine looking for birds or bats. He said there’s evidence that bats are attracted by turbines, and scientists also hypothesize that turbines could attract insects which would in turn attract bats.
This is an emerging science, and, Buler said, researchers haven’t yet eliminated many of the possible contributing factors.
Kevina Vulenic, in Delaware State University’s Department of Agriculture and Natural Resources, is looking closely at the results of the bat side of the study with an eye toward finding solutions to the bat deaths. One possible solution being studied is increasing the so-called cut-in speeds at which turbines are activated. That means the turbines wouldn’t start turning at lower wind speeds when bats are more likely to be flying. Buler said research coming out of the study indicates there could be a significant reduction in bat deaths by turning off the turbine when bats are more likely to be flying.
Willett Kempton worked with the University of Delaware’s College of Earth, Ocean and Environment Dean Nancy Targett and fellow researcher Jeremy Firestone to spearhead the Lewes turbine project. He said the turbine manufacturer, Gamesa, is working in cooperation with UD to develop a commercial product to place in turbines to reduce bat deaths. Kempton said, “It would take all the normal measurements being recorded by computers in the turbine - such as wind speed, temperature, time of year, time of day - and put that together with what we know about bat behavior.” Kempton said if the product determined that conditions were right for bats to be flying, it would automatically shut off the turbine, thus reducing potential bat deaths.
The bird and bat studies are two of many studies that drove the original installation of the Lewes turbine as one of the university’s most visible research projects. Others include corrosion impacts in a maritime setting and gear box wear over time. There was talk of a wind farm in the Delaware Bay with as many as 100 turbines. The question is, would it be a good site?
“Ornithologists told us we wouldn’t be able to predict what impact they would have on birds in advance,” said Kempton. “Birds are pretty good at avoiding things when they’re flying. Most of the deaths come from collisions in fog with high towers or against the windows of tall buildings. So, we’re doing the research in this area where there are so many migrating birds.
“We feel very bad about the osprey deaths, and the bat mortality is higher than we would like,” said Kempton. “But we see there are steps that can be taken to address those problems. The numbers we are seeing with bird deaths are about typical for a wind turbine. The bat numbers a little higher. Although none of our numbers show us out of compliance, we feel we should nonetheless manage the impacts. Still, when you look at the environmental benefit of turbines compared to environmental harm, the benefit from taking coal and gas facilities off line is many times greater than the environmental harm.”
Editor’s Note: To read a full version of the Justice Department’s press release regarding Duke Energy, click on the related information link below.