Predator exclusion fencing improves productivity at a mixed colony of Herring Gulls Larus argentatus, Lesser Black-backed Gulls L. fuscus and Great Black-backed Gulls L. marinus

Abstract

A large multi-species gull colony at South Walney in Cumbria, northwest England, has suffered declines over the past 20 years, and from 2016 to 2020 no gull chicks fledged despite up to 4,000 pairs of adults attempting to breed each year. The primary cause of nest failure was predation. In an attempt to reverse this decline, a predator exclusion fence was erected around the remnant gull colony in March 2021, and population and productivity surveys were carried out over the 2021 and 2022 breeding seasons. In 2021, 53, 27 and 40 chicks fledged from 263 Herring Gull, 186 Lesser Black-backed and 38 Great Black-backed Gull nests, respectively, resulting in reproductive success rates of 0.20, 0.15, and 1.05 fledglings per nest. Following the fence erection, in 2022 numbers of nesting birds increased by 151% overall to 575 Herring Gull nests, 553 Lesser Black-backed Gull nests and 28 Great Black-backed Gull nests, with reproductive success rates of 0.4, 0.61 and 1.21 respectively.