There's an owl in Tyrell's penthouse, but it's not an actual, natural owl. Like the replicants, it's artificial, even if it is an exact copy. You can tell that it's manufactured because the lenses in its eyes reflect light the same way Rachael's and the other replicants' do.

In Do Androids Dream of Electric Sheep?, the book on which Blade Runner is based, owls are the first creatures to go extinct when nearly all animal life dies out on earth. So that might be one reason for the presence of the owl in Tyrell's office (Tyrell also has a statue of an owl).

Also, the owl is a classic symbol of wisdom and knowledge. Tyrell, after all, possesses the secret, genetic knowledge that has allowed him to become a corporate overlord and creator of replicants. At the same time, the owl is famously considered a bird of ill-omen in many cultures throughout the world—which hints at both the wickedness of Tyrell and his impending death at Roy's hands.