Wind turbines pose a far more serious risk to bats than birds because their blades cause air pressure imbalances that can inflict fatal trauma.

A six-week study at two wind farms in the eastern United States recorded 1,764 and 2,900 bat fatalities. Another American project found that bat deaths outnumbered bird deaths in Montana by two to one. Though death rates in Europe are generally lower than this, extensive bat casualties have been reported in Britain.

Birds die when they are struck by turning blades, but bats use echolocation to evade this danger. However, they are at much higher risk than birds of barotrauma — a condition caused by sudden drops in air pressure. In May Natural England, a government agency responsible for wildlife protection, acknowledged increasing concern about the impact of wind farms on bat populations, and called for more research to ascertain the level of risk.

In mainland Europe, noctules, common pipistrelles and Nathusius's pipistrelles are most commonly recorded as casualties of wind farms. These species are listed by Natural England as high risk, together with Leisler's bats.

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