To Fly or Not to Fly?

S1 E1: David Attenborough takes us back through time to show how birds evolved from the dinosaurs and took to the air. When the early mammals were still quite small, birds ruled the planet, with mighty vultures cruising the skies and huge, flightless 'terror-birds' stalking the land. The island of New Zealand was isolated for so long without mammals that it became a true paradise for birds.