After I posted my email below I listened to sibley's sounds for mallards and it might have been male mallard courtship whistles.
> On Mar 19, 2017, at 9:34 PM, Suzanne Coleman <isooz...> [ILbirds] <ILbirds-noreply...> wrote:
> I was at a marsh tonight at nightfall and heard lots of whistles and piping sounds. I don't know what they were from. Any thoughts? It sounded like maybe even frogs but if so they haven't been there in past years that I recall. The birds I saw were mallards, shovelers, geese and I heard killdeer and snipe.
> Thanks for any suggestions.
> Suzanne Coleman