Surveys of the distribution and abundance of red-throated divers at the Kentish Flats wind farm during the pre-construction, construction and post-construction phases of the wind farm have been undertaken over 8 years prior to 2009-10. This report presents an analysis of new data sets from surveys completed at Kentish Flats during 2009-10.
The original statistical analysis carried out for the monitoring conducted under the FEPA licence of the effects of the Kentish Flats wind farm on bird populations utilised a BACI (before-after-control-impact) approach. However it was acknowledged in the monitoring reports that this was of relatively low power which meant that no statistically significant effect was identified although a qualitative assessment suggested an avoidance of the site by divers.
A previous review of the Kentish Flats monitoring programme data and reanalysis had shown that there has clearly been a notable decline in diver numbers within the wind farm/buffer zone following construction, at a time when the wider population (as determined from the aerial surveys) appeared to have been relatively stable, confirming the qualitative observations made in the previous Kentish Flats monitoring reports. There had been a statistically significant decrease in diver numbers within the wind farm site and its surrounds. There has not only been a decrease in numbers but also a shift in distribution away from the wind turbines, most markedly within 500m. This reduction in the wind farm site and 500m buffer was also apparent from the 2009-10 data. As noted in the previous report, the biological importance of such behaviour is not yet clear and needs to be addressed with reference to the context of the wider diver population within the Outer Thames Estuary.
There was some suggestion from the 2008-09 data in particular that the magnitude of the displacement may be decreasing through time; divers may be habituating to the presence of the wind turbines. The 2009-10 data did not suggest that the strength of any such habituation was increasing, though there were more diver records from within the wind farm site than there had been in 2008-09.
As noted previously, it is important to recognise that the results for this site may not be directly applicable to other wind farm sites given the Kentish Flats wind farm’s relatively small number of turbines and footprint size, and its relatively low importance for divers. It is possible, for example, that divers using a site of greater importance/attractiveness to them may be less likely to be affected by disturbance than those at Kentish Flats.