Population estimates for urban and natural nesting Herring Gull Larus argentatus and Lesser Black-backed Gull Larus fuscus in England (JNCC21_02)

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Joint Nature Conservation Committee was commissioned by Natural England to produce two reports that present provisional estimates of Herring Gull and Lesser Black-backed Gull populations in England and how these estimates were calculated. The accompanying report on Access to Evidence is linked below. Both reports have been independently reviewed by the BTO and ‘urban gull sub-group’ of the Seabird Census Steering Group.

This report provides current breeding population estimates for Herring Gull (HG) and Lesser Black-backed Gull (LG) in England. Estimates are also given separately for urban (roof-nesting) and rural (natural-nesting) populations, and for coastal and inland populations. HG and LB natural-nesting population estimates given are robust and comparable over time. Over the past 20 years, these HG and LB populations have declined -38% and -45%, respectively. Roof-nesting populations were more problematic to estimate. Two sophisticated extrapolation methods were employed, producing contrasting results with low confidence. Since ‘Seabird 2000’ likely under-estimated roof-nesting populations 20 years ago due to methodological issues that were subsequently identified, direct comparisons with results from either method employed here for ‘Seabird Count’, are unreliable. Notwithstanding these issues, roof-nesting populations of both species are likely to have increased over that period and results show for the first time that the greater proportions of HG and LB breeding population in England are now supported by the urban environment. Although ‘natural-nesting’ HG and LG populations have significantly declined, it is plausible that HG & LG populations in England overall have increased since ‘Seabird 2000’, but is not a conclusion that can be safely drawn from these results.

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Related Access to Evidence records

Title
Urban nesting Herring Gull Larus argentatus and Lesser Black-backed Gulls Larus fuscus population estimates: devising species-specific correction models for ground-based survey data (JNCC21_01)