First time I did the quest I couldn't get this knowledge.

Switched to an alt, killed an owl and came back with a cage, then accepted the quest and could get the knowledge from the NPC.

Completed the quest, no longer had the option to get knowledge.

You need a caged owl while the quest is in your quest log, but not completed.

It must be some kind of bug

Thanks for shareing this

I get knowledge too

So turns out you don't need to take the quest at all. You just need the caged owl in your inventory. I can't tell if you can turn it in for knowledge AFTER doing the quest though, but I did it without taking or doing the quest.