European eagle owl (Bubo bubo). The largest of all owls, the eagle owl can weigh in excess of four kilograms and have a wingspan of 200cm. Its diet ranges from rodents to small deer. This owl is found throughout much of Europe and Asia. Its presence in the wild in the UK has been reported occasionally throughout the last 300 years. It is not known whether eagle owls in the UK are escapees from captivity or if they have migrated here from mainland Europe.