In the five years that I've been photographing birds I've never seen a mallard trying to eat a frog, so this series is a first for me.
When I first spotted that this female had something in her mouth it appeared to be a water snake, since only one of frogs legs were visible at the time. Upon closer inspection it turned out to be a small frog.
After ten minutes of trying to swallow the frog, the mallard gave up. I suppose the mallard realized the frog was too large to swallow, or the latter escaped. There was no sign of the frog after it fell out of the mallard's mouth, so I can only guess its' fate.