TY - RPRT
TI - Further Use of Aerial Surveys to Detect Bird Displacement by Offshore Windfarms
AU - Maclean, I
AU - Skov, H
AU - Rehfisch, M
AB - Offshore windfarms are likely to become one of Europe's most extensive technical inventions in marine habitats. The areas in which windfarms are located often coincide with areas favored by large concentrations of seabirds. The UK Government has a legal obligation to monitor the impact windfarms might have on seabirds.This report follows a previous report commissioned by COWRIE (Maclean et al. 2006), in which the extent to which BERR (formally DTI) aerial survey protocol allows changes in bird numbers to be detected, was examined using power analysis. Changes in bird numbers can be hard to detect due to natural fluctuations in bird numbers. Power analysis allows a statistical assessment to be made of the probability that such changes could be distinguished from background fluctuations.Several issues are assessed in more detail than in the previous report. Rather than using data collected in many areas to estimate variability by assuming that the extent to which birds fluctuate in numbers is broadly similar (relative to the mean number present) across all sites, we select a few areas for which a long time-series of data exists and analyze these data exclusively. Additionally, rather than assuming a uniform decline within any given area, we explore one method of allowing for a gradient of decline, such that declines after windfarm construction are greatest closest to the windfarm. Lastly, we investigate the effects of using simple spatial variables (water depth, seabed slope gradient, seabed aspect, distance from land, distance from shallow water and seabed complexity) on the ability to detect changes in bird numbers. As with the previous report, four taxa were selected for analysis: red-throated diver (Gavia stellata), common scoter (Melanitta nigra), sandwich tern (Sterna sandvicensis) and lesser and great black-backed gull (Larus fuscus and L. marinus).Using long time-series of data rather than assuming equal proportional variability across many sites has no appreciable difference on the likelihood of being able to detect declines in bird numbers of 50% or less. The statistical power of being able to detect such changes remains low (
DA - 2007/10//
PY - 2007
SP - 46
PB - British Trust for Ornithology (BTO)
SN - COWRIE EXTDISP-06-07
UR - https://www.bto.org/research-data-services/publications/research-reports/2007/further-use-aerial-surveys-detect-bird-dis
LA - English
KW - Wind Energy
KW - Fixed Offshore Wind
KW - Displacement
KW - Birds
ER -