We have a Mallard Drake with no feathers on his chest. He hid under an evergreen for 2 days without coming out for water from our pond which is about 10 ft away from him. Yesterday he drank from the pond. He does not seem to be able to fly and is very weak. There is a large green feces stain at the edge of the pond which will wash into the pond where our grandchildren play. How concerned should we be?