Hmm, there is no united conformation on the origins of the owlbear(in lore, in real life we know Gygax based it on a toy). Dragons and other monsters are also magical creatures but still considered to be parts of nature in Faerûn. So a druid being against its existence just based on that feels wrong.
No, Owlbears are not magical beasts - they are, quite literally, Monstrosities. It's a creature type, with specific meaning and implications.
From the Monster Manual:
Monstrosities are monsters in the strictest sense — frightening creatures that are not ordinary, not truly natural, and almost never benign. Some are the results of magical experimentation gone awry (such as owlbears), and others are the product of terrible curses (including minotaurs and yuan-ti). They defy categorization, and in some sense serve as a catch-all category for creatures that don’t fit into any other type.
They aren't natural or part of any natural order.
"...netherese scouts and outriders destroyed the 3000 owlbears, creatures given existence by the creator races thousand of years ago" (Netheril:Empire of Magic, p. 10)
In the monster manual for 3.5 it was categorized as a magical beast, so that has been retconned since. And also, in the monster manual 5e their origin is debated.
So, I stand partly corrected. but then I guess we have to discuss what can be counted as natural in Forgotten realms since pretty much all there has been created by one thing or another. In a world where gods and other beings literally create things on a whim whenever they feel like it, natural does seem to be a bit loose term
. And yes, I'm aware that goes for real life as well depending on each one's beliefs.
