The actual word “mallard” used to just mean ‘a male duck’, a synonym of ‘drake’, though it is now predominantly used just for Anas platyrhynchos. It’s no real surprise there may have been confusion over what is, or is not, ‘a mallard’ though as the are quite unfussy about who or what they interbreed with, leading to the average collection of feral/wild ducks on an urban lake looking like it may be home to seven or eight different species.
Unusually these hybrids are often fertile, which means they can breed too. Generally hybrids are sterile. This leads to a range of colour variations as you can see in this picture.
Short of genetic testing, picking out what is or is not a mallard in here is pretty tricky.
We should talk briefly about feeding bread to ducks. Don’t do it. It isn’t natural food, fills them up, means they don’t get sufficient nutrients, and they can get diseases and deformities. Not only that, uneaten bread will breed bacteria and cause algal blooms that deplete oxygen from the water, potentially killing fish and amphibians. If you must feed the ducks, use something like corn. And if they aren’t hungry, don’t empty it in on the assumption they’ll eat it later.
To end on a more fun note, you may well have heard it said that Elvis Presley had his hair in ‘duck tails’, or a slightly less family-friendly version of that (duck’s bottom or similar). This is a reference to the upturned feathers on the male mallard. King of Rock ‘n’ Roll and a common fowl in the same blogpost. How often does that happen?