Pochard Aythya ferina use of chironomid-rich feeding habitat in winter

Abstract

The feeding distribution of pochard on 2 Buckinghamshire flooded gravel pits was studied when peak wintering numbers were present. On the deeper lake (mean depth 2.3 m) 99% of feeding occurred in the shallowest 10% of the lake, where depth averaged 1.6 m. In the shallower lake (mean depth 1.5 m) favoured feeding areas averaged 0.9 m deep. At this lake only 15% of the available habitat at this depth was used by feeding pochard, much shallower water being ignored. Chironomid larvae were present in significantly higher numbers and biomass/m2 in feeding areas. Pochard thus prefer to feed in shallow water and can select prey-rich areas, thus maximizing their food intake whilst minimizing their energy expenditure. -from Author