Contribution of non-native galliforms to annual variation in biomass of British birds

Abstract Millions of individuals two species non-native galliform birds, the Common Pheasant ( Phasianus colchicus ) and Red-legged Partridge Alectoris rufa are released into British countryside annually in late summer, supplementing established breeding populations these species. The biomass birds involved releases has been compared to bird biomass. However, validity this comparison is compromised because wild varies across year due reproduction, mortality migration. How Pheasants Partridges compares that other or whole year, currently unknown. Here, we produce estimates how assess contribution galliforms variation. We show overall probably lowest around start season April, peaks summer autumn. estimate a quarter contributed by Partridges, at their peak August represent about half all Britain.