Ducks Mimic Eating Motions

Shortly after feeding the ducks this afternoon, I noticed this unusual behaviour amongst a couple of mature female ducks. These are mature egg-laying duck hens. They have just finished eating when they began to mimic the sweeping motions of feeding with their beaks. Here are two videos showing this peculiar behaviour. The second video shows the ducks stretching their necks, moving their heads upwards.

I assumed it was part of a mating ritual but the first video might dispute this, where there is a mature male duck (drake) nearby, drinking from a plastic basin, and inadvertently pushing one of the duck hens aside, a bit of a scuffle ensuing.

Do you know what this behaviour means?