Studying bat migration routes: "Important for wind energy planning"

Wind turbine blades pose a deadly threat to small bats.

When the evenings grow mild and the winds are light, the protected species often hunt insects around onshore wind turbines. In such cases, certain turbines may need to temporarily operate in so-called bat mode or shut down briefly to reduce mortality.

"There is quite a bit of data on the weather conditions under which bats are active on land. Now, we also want to understand how they move across the sea. That’s important for the planning of offshore wind power,” says Heather Wood.

Swedish-Finnish research project

Since January, she has been a postdoctoral researcher at the Swedish University of Agricultural Sciences (SLU) Centre for Biological Diversity. There, she is part of the research project Bambi (Bat Migration Across the Baltic Sea). The aim of the project – a collaboration between Finnish and Swedish researchers– is to gain a better understanding of how bats migrate across the Baltic Sea.

“We know that bats migrate over the sea, but we want to learn more about when, where, how, and why. For example, it's interesting to know what weather conditions they fly in, whether they follow set routes, or move across a broader front,” says Heather Wood.

This knowledge is needed to inform decisions about the best placement of offshore wind farms, as well as whether they need to be shut down under certain conditions. Companies and authorities involved in this – such as the Swedish Environmental Protection Agency, several County Administrative Boards, and Vattenfall – are part of a reference group for the project.

“Migration season is a very sensitive period, and it could have major consequences for the entire population if large numbers of bats migrate along a route where they collide with large wind turbines,” says Heather Wood.

Deploying detectors

To track bat movements, she is analyzing already published materials through a meta-analysis of both reports and scientific studies.

She is also doing fieldwork. This spring, she is in the Stockholm archipelago setting up ultrasound detectors.

Project participants are placing such detectors on both the Swedish and Finnish sides of the Baltic Sea. Between April and November, these detectors will record bat sounds in the Stockholm and Helsinki