2006, Environmentally Sustainable Systems Ltd., Kentish Flats Offshore Wind Farm, Fourth Ornithological Monitoring Report series https://portal.medin.org.uk/portal/start.php?tpc=015_c695b912-6f3c-4cb8-b995-1042c621131f This Fourth Ornithological Monitoring report which covers Year 5 of an ongoing monitoring programme, presents and analyses the results of the 16 boat surveys from 7th December 2005 to 1st December 2006 for the Kentish Flats Wind Farm, and aerial data collected over four surveys from December 2005 to February 2006 in the area surrounding the wind farm. The purpose of this report is to meet the FEPA license monitoring requirements determined by DEFRA (following advice from English Nature, now Natural England) as a planning consent condition for the construction of the Kentish Flats project. Population estimates with means and standard errors for the wind farm site and buffer zone and for the control site have been calculated using the data collected during each of the 90 boat surveys since October 2001. Standard errors have been updated and improved by the larger (5-year) dataset. Relative abundance indices have been calculated with standard errors for all WWT aerial surveys covering Kentish Flats. The statistical comparisons of the boat and aerial survey data have not revealed any statistically significant changes in the abundances of bird populations (FEPA Objective 1) between the preconstruction, construction and operational periods. In particular the aerial data analyses provided no evidence of displacement of birds from the region that includes the Kentish Flats wind farm. As in previous years the boat analyses are somewhat restricted by the lack of comparable data from the control area, especially during the peak diver period, and the lack of consistency in the dates on which surveys were completed, together with the natural and in some cases extensive seasonal and interannual variation in the numbers and distributions of bird populations. Patterns of use and passage in and around the Kentish Flats wind farm, revealed by the mapped distributions of birds seen, do show some changes between years but in most cases it is not possible to attribute these changes to the construction or operation of the wind farm. In particular it is apparent that divers have not been seen within the wind farm site during the current reporting period and this may indicate some displacement of divers from the Kentish Flats wind turbine array. While no divers were seen within the operational wind farm a number were seen in flight or on the water very close to the outside edge of the wind farm, (some sitting less than 100m from a turbine). Even though no changes in bird abundance were statistically significant, the density estimates and mapped distributions suggest that the numbers of redthroated divers were lower during the operational phase than during pre-construction. Cormorant numbers were lower between December and April since the wind farm became operational, but not at other times of year. Lesser black-backed gull numbers in February were lower in the construction and operational phases. There were suggestions of differences in other months for this species and possible reductions for greater black-backed and herring gulls, but no consistent patterns were detected. Gannet and common tern numbers show no evidence of changes. As in the previous reporting period there was a suggestion from the surveyors reports that fewer common tern flights passed through the wind farm site (although no statistical difference in populations is apparent). The numbers of guillemot appear to be lower since the wind farm became operational. 20070619