Pen, The photo is what we called a "cookie duck". Mallard drakes have an irridescent green head and blue speculum bordered by white. Mallard hens are brown with the blue speculum. The white on this duck indicates a crossbred of a species with a domestic which is very common on ponds and lakes where a group is fed by people with breadcrumbs or leftover cookies, hence the moniker. They are most likely not migratory and very tame, hanging around for part of your lunch.