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5.3.21.2 Bio-season mean peak estimates 123. Razorbill is a species for which an overlapping occurrence of passage birds and more local breeding birds had been noted from an examination of the monthly occurrence of the data. The biological mean peak abundance estimates contain an apportionment to account for this overlap, though monthly mean peak estimates for this species before this apportioning across bio-seasons is contained in Appendix B.
124. Numbers peaked during the winter bio-season when an estimated 1,536 individuals were present within the East Anglia THREE site, with an estimated 5.04 birds / km2 (Table 5.44). A similar abundance occurred during the spring migration season, with 1,504 individuals present. Although both wintering and spring migration season mean peak abundances were below the regional 1% threshold both have been considered of regional importance, as proportionately the numbers were only marginally below the thresholds. Monthly densities of razorbills within the East Anglia THREE site and East Anglia THREE site with a 4 km buffer are presented in Appendix 3. Mean peak abundance estimates for spring migration bio-season indicate that razorbills are of regional importance in the East Anglia THREE site only (Table 5.45).
Table 5.44. Bio-seasonmean peak abundance estimates and mean peak densities of razorbills within the East Anglia THREE Site only.