A new Danish study has designed a risk management tool to identify the most vulnerable bird species in relation to collisions with the wind turbines. Two indicators are used in the framework: the relative abundance of breeding populations of birds potentially affected by a wind farm and the vulnerability of a species to death from collisions with wind turbines. Combining both these indicators into one index (the 'Environmental Sensitivity Index') allows the risk to different species to be classified as low, medium or high priority. A case study, demonstrating the use of the framework, was based on the large Nysted wind-farm off the coast of Denmark. The area is considered to be a migration hotspot, with thousands of geese and ducks and substantial numbers of migrating birds of prey and passerines (mostly land birds) passing through the area during the autumn migration. Of the 38 species under investigation, birds of prey and waterbird populations were most at risk of suffering as a result of collisions with the wind turbines. These species tend to be long-lived, mature late and lay few eggs, all of which affect the adult survival rate, and consequently the growth of a population. These two groups represented 53 per cent of all the species in the study. Another 34 per cent of the species were at medium risk. Only passerines showed a low risk from wind farms. For individual species of birds, the tundra swan and barnacle goose were found to be the most at risk from the windfarm. The hirudines (swallow and martin family) and Eurasian siskin were the least at risk. The 15 most abundant species flying past the windfarm were all birds of prey, waterbirds and hirudines. The framework can be used: � by planners who need to identify which bird species need further impact studies; � to assess the cumulative effects of multiple wind farms; � to help decision-makers make better use of limited resources when planning wind farms developments by understanding which bird species are most at risk; and � for the assessment of bird collisions with other obstacles, such as tall buildings, power lines, telecommunication towers and aircraft.