Its pretty obvious what happened here .The duck came across this fella struggling in deep water and to help him out he 'toad' it to the other side . Or -Opportunity mate ,plain and simple .I kept fancy pheasants in an avary once and was surprised one day ,to watch a golden pheasant hen chase ,catch and eat a full grown woodmouse that was in the feeder .Mouse was still wriggling in the birds crop .