duckluck,
I remember working in eastern Ohio, where a certain type of fescue was planted. This fescue would become infected with a fungus - an endophyte - and eating infected fescue caused fertility and birthing problems with horses. What a world!
Thanks for the links, fellow duck lovers . . . I have been trying to find confirmation that jewelweed, Impatiens capensis is okay for ducks. It is on a list of plants that attract ducks, and it often grows at waters' edge. I think it will be okay, but it would be nice to be sure before letting them have any!
I plant buckwheat as a cover crop between garlic plantings. So I have some on hand. I was thinking of making a frame with poultry fence over it, and laying it over a bed of buckwheat to let it grow up through the fence . . . . another project!!! Buckwheat, by the way, is easy to grow, sprouts quickly, and if you let it keep growing, makes pretty little white flowers that bees adore.