There's also homo sapiens and Sequoiadendron giganteum, along with various other grasses, flowering plants, trees, etc. There's no particular reason to believe that anatidae (or a similar family with enough morphological similarity that "duck" adequately translates whatever name they bear in Galactic Basic) don't exist anywhere in the known Star Wars galaxy. I'd certainly expect them to have evolved on at least one of the thousand-thousand worlds that make up the Empire, along with one of everything else that we know here on Earth. (Except the platypus. That bizarre thing doesn't even belong in sci-fi.)
It could be worse. Lucas/Foster could've gone the Hubbard route and called them "water-swimming birds" or "oil-feather birds."