Usually these discussions only talk about the English. I would like to know if in Dutch also is it more natural to say "Eenden zijn vogels." without the article? Italian would keep the article even for things (the things) in general but I suspect Dutch follows the English pattern.
I guess we lose "The" from sentences when we're talking about an unspecific amount of animals. If I owned five ducks I could say "The ducks are eating their lunch" but if I was talking about ducks across the world I'd say "Ducks eat bread". However if my ducks ate something unusual I might say something like "These ducks eat bananas."
This sentence is quackers. It would be better if it were "Ducks are birds." "The ducks" means we are referring to certain or specific ducks, and we mean that those certain ducks we are referring to are birds, thus implying that the rest of them aren't. It doesn't make sense. Please change.