Our Changing World - Saddleback song

North Island saddleback - or tieke - are one of New Zealand's conservation success stories. By the 1960s they were found on just a single island, Hen Island in the Hen and Chicken group near Whangarei. But since then they've been successfully moved to a number of different islands and mainland sanctuaries, including Tawharanui Regional Park north of Auckland. And, as birds were moved from one island to another, biologists noticed that interesting changes to their songs were taking place. That's because birds learn song in the same way that we learn language - by listening to other people, and imitating them. And, as song bird expert Kevin Parker tells Alison Ballance, when you don't have any neighbours to copy you have to invent your own song.