Movements of wintering diving ducks: new insights from nasal saddled individuals

Abstract

Capsule In winter diving ducks commonly move between wetlands more than 100 km apart, but short-distance daily movements dominate their activity. Aims To describe the movements of Common Pochards Aythya ferina and Tufted Ducks Aythya fuligula during the wintering season in France and to investigate intrinsic and extrinsic factors potentially affecting the direction and distance of these movement. Methods Distances, directions and patterns/strategies of winter movements were assessed from a combination of encounter data: physical recaptures at the ringing site, re-sightings of individuals fitted with nasal saddles, and ring recoveries of dead individuals. Results Patterns of movements derived from multiple locations (i.e. successive re-sightings) of individuals could be assessed, showing that several ‘strategies’ may coexist in the same species (residency, exploitation of two wintering sites with or without return journey, and exploration of several sites). Individuals may use several sites more than 100 km apart during a given winter. Interestingly, directions of movements did not fit any previously observed pattern, especially in Common Pochards, whose movements tended to be biased towards the northeast at the beginning of the wintering season (October–November) whereas south or southwest movements were expected. Weather conditions in winter affected directions of movements in Common Pochards; eastwards movements towards ice-free Alpine lakes were more frequently observed during cold spells. Conclusion Overall, our results suggest that exchanges of birds between wetlands more than 100 km apart are rather common even though short-distance movements related to daily activities are dominant. Our study provides new insights into the potential origin of ducks suspected of spreading infectious diseases.