Wind energy in addressing greenhouse gas emissions and high energy reliance is considered to be a stable strategy. However, wind power construction has a negative effect on nature conservation, environment and survival of wild animals, especially for the avian species. It is reported that millions of birds being killed by wind turbine every year around the world, the wind farm may also affect migratory birds and habitat utilization. Wind farms located on the route of migratory birds could bring enormous threats to bird migration, also, wind farm development could cause much habitat reduce and make the birds facing greater threats. Specific geographical conditions, the environment of wind farms and the characteristics of bird species are the main causes of the bird collision. Reasonable siting of wind farm before construction, the proper use of mitigation measures and compensation measures after the construction can effectively reduce the impact of wind power development on birds and other wildlife. This paper mainly introduce the influences of American and European wind farms on birds, summarize the causes, and discuss the strategies on how to reduce bird collisions in wind farms.