In NY I worked on a shooting preserve,dog handler,Didn't get paid but it was too much fun working the dogs.
They raised over 5,000 mallards from 1 day old. These birds were never penned but raised on a lake and fed generously. Each mallard had one ehind toe cut off when it was just days old.The lake was hand dug during the depression and was shaped like a long U.
The birds were fed on a beach that had a large trap door built on it, when it was time to hunt the trap was dropped, catching hundreds of birds inside the fenced in area.
The birds were gently herded into one corner with a small hole in the fence. Long boxes were aligned from this door, each box had a drop door at both ends and both were pulled out ,creating a long tube for the trappped birds to run into. When the birds were all in the tube the trap doors were dropped and birds taken out of the top door on each box. Thes birds were examened for the missing tow and if they were one of ours they went into a transport box. All other ducks were thrown away to fly away. Other birds learned to mooch of our free grain and some hung around all year.
The birds in the transport boxes were taken away to be released. The would fly right back to the lake and this time there were hunters in blinds all around the lake. Every 50 released birds ,or so, the game keeper would blow a horn and all shooting would stop. The hunters would relocate to a new blind and then the hunt capt. blew a horn and another 50 birds were thrown.
After the last shoot of the season the feeding stopped and the mallards just went away.The bird breeder was very careful to keep his stock wild. He had clipped wing females and the breeders flew in from where-ever. Why bother to feed males when he could get the job done for free?
Sorry for the long letter but if you ever shoot a "wild" mallard with a small hind toe missing thank a shooting preserve.