英语中有两个习语：as stupid as an owl 和 as wise as an owl，在

英语中有两个习语：as stupid as an owl 和 as wise as an owl，在

代表着智慧吧
I had not, until today, ever come accross "as stupid as an Owl", but it does exist. In "Rose in Bloom" by Louisa May Alcott, there is the line "But I look as sober as a judge and as stupid as an owl by daylight". Perhaps this might explain it. After all Owls are often considered (incorrectly as it goes) to be nocturnal birds and may therefore "appear" stupid in daylight.
Other than this, Owls are considered to be somehow "wise".
It must be said though that an Owl is neither wise, nor stupid, it is simply a bird.
Owls have a very solemn bearing. This makes them seem wise. In AE, we say "wise old owl." There is even a brand of potato chip called Wise which uses the image of an owl in its marketing.

Sometimes people who are not wise put on airs of being wise. They are also solemn, but stupid. Referring to such people as owls is either out-moded or a Britishism, I'm not sure. Check with a Brit. But the OED quote Leigh Hunt writing in 1847: "It vexes one to see so fine a poet make such a

poet make such an owl of himself."
It's not necessarily an English expression only. In Finnish we use the equivalent of owl as an adjective meaning stupid.