Misty the duckling's mysterious disappearance has stressed out other ducks in the group, who were so upset they refused to eat for two days.
Owner Chris Gunnill said there had been no sign of a fox and cannot explain where Misty has gone.
He has asked people in Lowton, Greater Manchester, to look be on the lookout for the missing bird.
"The other ducks were dead depressed for two days," he said.
"They were quacking and they didn't eat."
Misty, an Indian Runner duck, disappeared on Wednesday and would now be about twice the size it appears in the photos.
The duckling was living at Lime House in Lowton, where Mr Gunnill runs a garden project for adults with learning disabilities and mental health issues.
"We only had one duckling left from only two hatched as the other eight eggs were still-born deaths, so you can see how important this one little duckling was to us.
"It's a mystery, as we have no clues to its disappearance."
The chickens and ducks are kept for their eggs, Mr Gunnill said.
He said the birds also help to calm people down.
"When you've got someone with a mental health issue, you stick a chicken in someone's hands or duck near them and it can potentially calm them down straight away," he said.
A reward of free range eggs for life is being offered for the return of a pet duckling missing for almost a week.