The causes of diving duck population declines on Lough Neagh, Northern Ireland

Lough Neagh Special Protection Area (SPA) was one of the most important non-estuarine sites for overwintering wildfowl in Britain and Ireland. Up to 100 000 diving ducks overwintered at the site during the early 1990s, however, by the winter of 2003/04, populations of pochard (Aythya ferina), tufted duck (A. fuligula), scaup (A. marila) and goldeneye (Bucephala clangula) had declined to 23 500 individuals. The changepoint in the temporal trend was the winter of 2000101 with the declines occurring rapidly within 2 winters. Comparable declines were observed in some resident and partially resident species. The density and biomass of benthic macro invertebrates, the main food source of diving ducks, declined by 66-67% between 1997/98 and 2010. This reduction was correlated with a major decline in chlorophyll a concentrations, suggesting a shift in the Lough Neagh ecosystem coincident with the changes observed in the bird community. However, there was no substantial shift in the diving duck diet comparable to the shift observed in the availability of their prey. Stable isotope analysis of duck tissue collected throughout 2010-2012 suggested that 57% of birds, mostly 1 st winter birds, had fed recently on other waterbodies, indicating high levels of dynamic within-winter movements and population redistribution. Analysis of ringing and recovery data provided support for the phenomenon of migratory short-stopping in goldeneye; however, this was not the case for the other species Neve11heless, a meta-analysis of count data suggested rapid climate-driven shifts in the wintering distributions of tufted duck and goldeneye in response to increasingly mild winter temperatures. It is concluded that intrinsic and extrinsic factors coincidentally conspired to make Lough Neagh a less attractive overwintering site, leading to a marked decline in diving duck numbers after the winter of 2000/01.EThOS - Electronic Theses Online ServiceGBUnited Kingdo