This National Geographic article describes how feeding ducks bread is actually harmful. Among the items listed as safe to feed to ducks it lists corn. Does this mean that cornbread is an acceptable alternative to regular bread?
Cornbread may contain wheat flour as well as corn meal. Both are processed cereals and so should not be given to wild creatures.
In addition cornbread probably contains some of these ingredients:
Tempting as it might be to feed wild creatures, they should only be fed food they would normally eat. In addition, once you start feeding them the habitat will be able to host more creatures than it would support naturally. So if you stop feeding them, many will die.
In a park there may be many random people feeding the ducks, who come and go, and so the duck population may stabilise.
But when feeding wild birds in your garden in winter you must continue as they will be relying on you.