Eurasian eagle-owl
Even those near the northern limits of their range, where winters are harsh and likely to bear little in food, the eagle-owl does not leave its native range. There are cases from Russia of Eurasian eagle-owls moving south for the winter, as the icebound, infamously harsh climate there is too severe even for these hardy birds and their prey. Similarly, Eurasian eagle-owls living in the Tibetan highlands and Himalayas may in some cases vacate their normal territories when winter hits and move south. Even in those two examples, there is no evidence of consistent, annual migration by Eurasian eagle-owls and the birds may eke out a living on their normal territories even in the sparsest times.
Eurasian eagle-owl
The Eurasian eagle-owl at one time occurred naturally in Great Britain. Some, including the RSPB have claimed that this was probably by about 10,000–9,000 years ago after the last ice age but fossil remains found in Meare Lake Village have indicated the eagle-owl occurring as recently as roughly 2,000 years ago in the fossil record. The lack of presence of the Eurasian eagle-owl in British folklore or writings in recent millennium may indicate the lack of occurrence by this species there. The flooding of the land bridge between Britain and continental Europe may have been responsible for their extirpation as they only disperse over limited distances, although early human persecution presumably played a role as well. Some reportages of eagle-owls in Britain have been revealed to actually be great horned owls or Indian eagle-owls, the latter a particularly popular owl in falconry circuits. Some breeding pairs do still occur in Britain, the exact number of pairs and individuals is not definitely known. The World Owl Trust stated that they believe some eagle-owls occurring in North England and Scotland are naturally occurring, making the flight of roughly from the west coast of Norway to Shetland and the east coast of Scotland, as well as possibly from the coasts of the Netherlands and Belgium to the south. Although not migratory, eagle-owls can disperse some notable distances in young birds seeking a territory. Prior studies of eagle-owl distribution have indicated a strong reluctance to cross large bodies of water in the species. Many authorities state that the Eurasian eagle-owls occurring in Britain are individuals that have escaped from captivity. While, until 19th century, wealthy collectors may have released unwanted eagle-owls, despite press to the contrary, there is no evidence of any organization or individual intentionally releasing eagle-owls recently with the intent to establish a breeding population. Many feel that the eagle-owl would be classified as an "alien" species. Due to its predatory abilities, many, especially those in the press, have expressed alarm of their effect on "native" species. From 1994 to 2007, 73 escaped eagle-owls were not registered as returned, while 50 escapees were re-captured. Several recorded breeding attempts have been studied and most were unsuccessful, due in large part to incidental disturbance by humans and some due to direct persecution, with eggs having been smashed.