Influence of grain characteristics on optimal diet of field-feeding mallards Anas platyrhynchos.
The relationship between cereal preference and rate of energy intake was studied for the mallard and 4 types of cereal grain. In a field experiment at a Wildlife Management Unit in Saskatchewan where wheat and barley were extremely abundant, wild mallards tended to feed more often in, and depleted grain more rapidly from barley than from 2 varieties of hard spring (hard-kernel) wheat. In a laboratory study, mallards chose unthreshed durum (soft-kernel) wheat and barley over 2 varieties of hard spring wheat. Mallards removed kernels from heads (i.e. ears or cereal spikes) of barley and durum wheat faster than from hard spring wheat, and thereby ingested energy more quickly. However, when kernels were removed from the heads the preferences changed and mallards ate more hard spring wheat, followed by durum wheat, then barley. Findings suggest that rate of energy intake rather than energy content is most important to cereal choice by field-feeding mallards, and possibly to other animals involved in crop damage. Thus, practical modifications to cereal grains which reduce animals' feeding efficiencies offer some promise for alleviating crop damage.