Abstract Wind power is increasingly being used worldwide as an important contribution to renewable energy, due to its low greenhouse gas emissions compared to fossil fuels. However, it has been suggested that the development of wind power has caused an adverse impacts on birds. We summarise current evidence of bird fatalities resulting from wind power, outline the reasons why and how birds are killed by wind power developments, and identify research needs to better inform researchers, decision makers, developers and other stakeholders, to help mitigate any adverse impacts of wind power developments on birds.