A Kookoburra that won't open it's beak!

["Anthony Smith" <>]

A local vet has had a Kookoburra that won't open it's beak brought in.

The bird has no signs of injury as is still fit and flying. It tries to eat 
food but doesn't open it's beak. Under anesthetic the beak opens without 
resistance and with no sign of broken bones (grinding etc). There is no 
swelling near the beak. There was nothing caught in it's throat or crop and no 
signs of irritation.

Has anyone any ideas about what might be ailing the bird?

Thanks and regards,
Anthony Smith