An important element of the environmental impact assessments for offshore wind farms is the potential for interactions with seabirds, particularly through collision of birds in flight with rotating blades. In many cases, these birds are protected through Natura regulations, and Appropriate Assessments are required of the responsible authorities. Traditional models of collision (the “Band model”) make use of the numbers or density of birds flying at turbine height (i.e. within the swept area of the turbine blades). In the UK, the minimum clearance of the blades above the water is normally 22m above HAT. Recent compilations of flight height information indicate that, for some species, most birds at risk of collision are flying in the lower part of the swept area. For such species, increasing the clearance above the water surface can significantly reduce the number of flights exposed to collision risk. Modelled distributions of flight heights for a range of species have been used to estimate the reduction in collision risk achieved by increasing clearance of turbine blades above the water. While it is recognised that there will be additional engineering and cost considerations involved in adopting greater clearance heights, increasing the clearance in areas of importance to seabirds may reduce the constraints on wind farm development arising from concerns over potential collisions with birds in flight. The ability to manage collision risk in this way adds a new dimension to the expressions of risk available to marine planners, and could lead to new formulations of development strategies.