An Investigation of Diving Ducks’ Predation on Dreissena polymorph to Determine the Size Preference of Zebra Mussels Consumed by Waterfowl

ABSTRACT
The predation of diving ducks on Dreissena polymorpha was investigated to determine which size of zebra mussels are most commonly preyed upon by waterfowl. The gizzard contents of various species of ducks from Point Pelee Ontario were examined for mussel shell fragments to determine the mussel size consumed. The data was compiled to calculate an average mussel size and the amount of predation on each size by ducks. Waterfowl fed preferentially on zebra mussels of moderate size with a mussel size of 16mm being optimal. The delicate balance between energy expenditure and consumed food energy along with the threat of kleptoparasitism guide waterfowl to feed upon mussels around 16mm. ...