purple windmill
A study has revealed that a wind turbine’s colour affects how many insects it attracts, shedding more light on why the turbines occasionally kill bats and birds. Scientists say that turbines, most commonly painted white or grey, draw in insects. These then lure bats and birds – as they pursue their prey – into the path of the turbine blades. Support for the idea comes from another study showing that bats are most often killed by turbines at night and in summer, when insects are most abundant.
Bats are more likely to be killed by wind turbines at night and during the summer, researchers have discovered. The reason is thought to be because the turbines attract migrating insects. At some sites, 20 to 40 bats are killed each year per turbine, although rates of one to three bats are more typical.Now scientists have ascertained that 90% of bat mortality occurs in northern Europe between late July and early October. A similar pattern occurs in North America. Observations from both continents also show that most bats are killed on relatively warm nights with low wind speed.
While the review by scientists does not provide all the answers, it suggests wind turbines are tall enough to attract insects migrating at night, which typically fly at heights of over 60m. Bats and birds are then killed by turbine blades as they feed on this insect bonanza.
PhD student Chloe Long of Loughborough University, UK. and her Loughborough colleagues, Dr James Flint and Dr Paul Lepper, conducted the first empirical study of insect attraction to wind turbines, the results of which are published in the European Journal of Wildlife Research.
In particular, they measured how a turbine’s colour alters how many insects gather around it. Most turbines are painted pure white or light grey, in a bid to make them as visually unobtrusive as possible. But insects, it seems, are unlikely to ignore these muted tones. The researchers measured how many insects were attracted to a range of paint colours, including pure white, light and dark grey, sky blue, red and purple.
Turbines painted pure white and light grey drew the most insects bar just one other colour; yellow. The colour they found least attractive was purple.
EUROPEAN JOURNAL OF WILDLIFE RESEARCH
The researchers also found that the ultraviolet and infrared components of paint colour, which humans cannot see but insects can, also had a significant impact, with higher levels of both attracting more insects.
Insect attraction to wind turbines: does colour play a role? by C. V. Long, J. A. Flint and P. A. Lepper
Mortality of bats at wind turbines links to nocturnal insect migration? by Jens Rydell, Lothar Bach, Marie-Jo Dubourg-Savage, Martin Green, Luísa Rodrigues and Anders Hedenström
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