Michael Palin presents the iconic bald eagle from Alaska. In days of yore, when bald meant "white" rather than hairless, these magnificent birds with a two metre wingspans were common over the whole of North America. They were revered in native American cultures. The Sioux wore eagle feathers in their head-dresses to protect them in battle and the Comanche celebrated the birds with an eagle dance.

The bird became a national symbol for the United States of America and on the Great Seal is pictured grasping a bunch of arrows in one talon and an olive branch in the other.

But pomp and reverence don't always guarantee protection. In 1962 in her classic book "Silent Spring", Rachel Carson warned that bald eagle populations had dwindled alarmingly and that the birds were failing to reproduce successfully. Rightly, she suspected that pesticides were responsible. Bald eagle populations crashed across the USA from the middle of the twentieth century, but fortunately are now recovering following a ban on the use of the offending pesticides.