Northern gannets avoid windfarms during their autumn passage period, research using high resolution digital stills gathered during aerial surveys suggests.

This indicates that many fewer birds than previously thought will collide with turbine blades in offshore wind farms and that earlier assessments have tended to be overly precautionary. The research was carried out by APEM on behalf of East Anglia Offshore Wind.

Gannet in flight

Developing a new approach

APEM developed a new approach for estimating how likely Northern gannets are to avoid wind farms, both close to the turbines and further away. Researchers analysed aerial photographs in order to record how many gannets were found at different distances from the Greater Gabbard offshore wind farm.

APEM carried out four aerial surveys of the wind farm in late 2014, a period when large numbers of Northern gannets are in passage off the East Anglian coast and in the southern North Sea.

Digital images were collected by planes flying at over 300 m in order not to disturb the birds. In total, 336 gannets were recorded in the images, of which eight were recorded within the wind farm area and 328 were recorded outside it.

The gannets had minimum recorded approach distances of 443 m and 359 m away from the nearest turbine within and outside the footprint, respectively.

Collision risk modelling

In the UK the prediction of the possible numbers of flying birds that collide with the moving blades of a wind farm is usually carried out using the Band collision risk model

The final stage of the modelling process is to apply an avoidance factor. This single figure accounts for the behaviour that a flying bird might exhibit when encountering the constructed wind farm in order to avoid colliding with the turbines.

Such avoiding actions might be taken at some distance from the wind farm, on a close approach to the outside of the wind farm, or on a close approach to the moving turbine blades.

Based on their research, APEM’s ornithologists suggested that an avoidance factor of 99.5 per cent would be reasonable. This suggests that many fewer gannets would collide with wind turbine blades than previously estimated, and thus lessen wind farm consent risk.