Photo by Wolfgang Kippes
The caption called this a sperlingskauz, which was translated to "Sparrow Owl."
I'd never heard of a Sparrow Owl, but the EPO has a scientific name that is Latin for "Sparrow Owl" that I will assume is how it got its German name.
That's one of my favourite 'flat jokes' (Flachwitze in German).
Ah, I was finally able to figure out the "joke," as I only got the "flat" earlier as I didn't know "huhu." I had just searched for "eulenwitz," and this thing popped up a million times. I knew "uhu" but I was too tired yet to notice the extra H to figure it was a pun. I knew one of you would lead me to the answer though!
For everyone not in on it:
Was sitzt auf einem Baum und winkt? — Ein "Huhu“! What is sitting on a tree and waving? – A “Huhu”!
Explanation: in German, “huhu” is a greeting, while “Uhu” signifies an “owl”
From The ~~Funniest~~ One and Only Multi-Language Jokebook
You beat me to it! I also added an explanation in a comment. It's quite cute :D
Your explanation has more details, so it's still the better one.
Plus you taught me about flat jokes, so I got to read a few more looking for the owl explanation.