Shag or cormorant?

Apparently the pied shag (Phalacrocorax varius varius) used to be known as the “yellow faced cormorant”. I don’t understand why some of these names are chosen. Sure, the pied shag has a fleshy yellow patch in front of its eyes, but it stretches it a bit to say it’s the bird’s whole face that’s yellow. And that bit of the face is yellow for only a few brief months of the year, for the rest of the year, people would look at them and go “Yellow faced? Who names these things?” The “pied” in the pied shag’s name tells you something about it: It has clearly defined areas of black and white. As for the shag versus cormorant issue, the terms are used pretty much interchangeably for members of the family Phalacrocoracidae. Members of the family with a crest tend to be called shags rather than cormorants, but our pied shag doesn’t have a crest. Bird naming… it’s the wild west.