Way back in the 17th century, England's King Charles II decreed there always be six ravens at the Tower of London.

The legend is that if the birds were ever to leave the tower, the White Tower would crumble, and England would pretty much follow suit.

As you can see, when the fate of a nation of 55 million is at stake, serious measures must be taken to protect the ravens from emerging threats like bird flu.

For the time being, that means keeping them inside in specially builty aviaries.

Here's the AP story on CTV.ca.