BRANTA — Irena Tománková

Causes of diving duck population declines on Lough Neagh, Northern Ireland

Institution: Queen's University Belfast, UK
Supervisors: Neil Reid, Chris Harrod, Tony Fox
Details: PhD 2013 (Completed)

Address: Queen's University Belfast, School of Biological Sciences, MBC, 97 Lisburn Road, Belfast, BT9 7BL, UK. (2014) Email

Subject Keywords: Diving ducks, Lough Neagh, SPA, population trends, benthic macroinvertebrates, food availability, EURING, climate change, migratory short-stopping, diet, stable isotope analysis
Species Keywords: Common Pochard, Aythya ferina, Tufted Duck, Aythya fuligula, Greater Scaup, Aythya marila, Goldeneye, Bucephala clangula

Thesis online at https://www.qub.ac.uk/sites/Quercus/Filestore/Filetoupload,419200,en.pdf

 

Abstract

Lough Neagh and Lough Beg Special Protection Area (SPA) was one of the most important non-estuarine sites for overwintering wildfowl in Britain and Ireland. Up to 100 000 individual 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 2000/01 with most of the decline occurring rapidly within 2 winters. These changes in migratory species may implicate extrinsic factors at the flyway-scale yet comparable declines in resident or partially resident species, such as coot (Fulica atra) and mute swan (Cygnus olor), may also implicate intrinsic factors. The density and biomass of benthic macroinvertebrates, 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, taken here as a proxy of primary productivity, suggesting a major shift in the Lough Neagh ecosystem coincident with the changes observed in overwintering bird communities. However, there was no substantial shift in the diving duck diet (derived from oesophagus contents) comparable to the shift observed in the availability of their prey. Stable isotope analysis of duck liver tissue collected throughout 2010-2012 suggested that 57% of birds, mostly 1st 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, where distances between their breeding grounds and winter recovery locations had contracted by 400km from the south-west to north-east Europe. However, this was not the case for the other species. Nevertheless, a meta-analysis of count data suggested rapid climate-driven shifts in the wintering distributions of three common waterbird species including tufted duck and goldeneye in response to increasingly mild winter temperatures, making waterbodies at northern latitudes more suitable as overwintering sites. 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 shortly after the winter of 2000/01.

 

Publications

Lehikoinen, A., Jaatinen, K., Vïhïtalo, A.V., Clausen, P., Crowe, O., Deceuninck, B., Hearn, R., Holt, C.A., Hornman, M., Keller, V., Nilsson, L., Langendoen, T., Tománková, I., Wahl, J. & Fox, A.D. 2013. Rapid climate driven shifts in wintering distributions of three common waterbird species. Global Change Biology 19: 2071-2081.
Tománková, I., Boland, H., Reid, N. & Fox, A.D. 2013. Assessing the extent to which temporal changes in waterbird community composition are driven by either local, regional or global factors. Aquatic Conservation: Marine and Freshwater Ecosystems 23: 343-355.
Tománková, I., Harrod, C., Fox, A.D. & Reid, N.. 2014. Chlorophyll-a concentrations and macroinvertebrate declines coincident with collapse of overwintering diving duck populations in a large eutrophic lake. Freshwater Biology 59: 249-256. View abstract
Tománková, I., Harrod, C., Kunc, H.P. & Reid, N. 2013. Gizzard contents and morphometrics of overwintering diving ducks shot at Lough Neagh. Irish Naturalists’ Journal 32: 76-77.
Tománková, I., Harrod, C. & Reid, N. In press. Temporal changes in the diet of Tufted Ducks Aythya fuligula overwintering at Lough Neagh. Irish Birds.
Tománková, I., Kelly, R. & Reid, N. 2013. Assessment of commercial sand barge radars for detecting overwintering diving ducks at Lough Neagh. Irish Birds 9: 559-562.
Tománková, I., Reid, N., Enlander, I. & Fox, A.D. 2013. Ringing and recovery data prove poor at detecting migratory short-stopping of diving ducks associated with climate change throughout Europe. Ringing & Migration 28: 30-38.
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