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APPENDIX CIII: CORRECTED MONTHLY MEAN PEAK ABUNDANCE ESTIMATES AND BIRD DENSITIES FOR GUILLEMOT AND RAZORBILL IN EAST ANGLIA THREE SITE ONLY (INCLUDING ATTRIBUTION OF UNIDENTIFIED BIRDS)
The tables contained within Appendix Ciii present corrected monthly peak population estimates, corrected mean population estimates and the corrected bird densities associated with those populations within the East Anglia THREE Site only for species that are subject to availability bias (common guillemot and razorbill). The population estimates are presented to species level only and include any attribution of unidentified ‘guillemots/razorbills’ into the monthly population estimates and densities (Tables 3.45 and 3.46). The application of a correction factor is to account for an availability bias due to the snap shot nature of aerial surveys not recording birds underwater at the time of aerial image gathering. The correction factor has been applied to the total birds recorded (sitting and flying) as very few birds were recorded as flying, therefore a further layer of precaution is contained within the corrected totals for environmental impact assessment purposes.
The correction factor applied to each species follows the methodology used for East Anglia ONE ((APEM (2013) East Anglia ONE Offshore Windfarm: Addendum to the Ornithology (Marine and Coastal) Chapter of the Environmental Statement. APEM Scientific Report 512763 – 01). This applies a correction factor on the basis of aerial surveys recording 87% of sitting common guillemots and 89% of sitting razorbills, as 13% and 11% respectively, of these species will be underwater when aerial imagery is captured. Therefore to correct for availability bias the ‘unavailable’ birds are added to the bird totals on a monthly basis to create revised population estimates. The revised population estimates for common guillemot and razorbill for the Site and Site plus 4 km Buffer are presented in Tables 3.47 and 3.48.