Identifying habitat-driven spatial variation in colony size of Herring Gulls Larus argentatus

Capsule: Spatial clustering was observed in colony growth rates of three large UK gull species with proxies of local marine and intertidal resources explaining part of this variation in two species. Aims: To investigate spatial clustering in colony growth rates of three gull species and determine which environmental variables may explain any spatial clustering observed. Methods: Colony growth rates were calculated for Herring Gull Larus argentatus, Lesser Black-backed Gull L. fuscus and Great Black-backed Gull L. marinus to identify spatial 2synchrony and to relate to proxies of local foraging conditions in coastal habitats. Results: Spatial clustering in growth rates was found in the gull species. Herring Gull colonies located in areas with greater availability of intertidal prey and fishery activity had higher growth rates. Lesser Black-backed Gull colonies in areas of higher chlorophyll a concentrations experienced more negative growth rates suggesting a negative effect in areas of potential local runoff from agriculture and built-up areas. Conclusion: Spatial clustering in the gulls’ colony growth rates indicated that local colonies did experience similar environmental conditions; helping identify variables influencing coastal populations of two gull species, highlighting the importance of marine habitats. These results highlight the need for species and area-specific management for these species of conservation concern