In the 25th year of the BBC's Natural History Unit-a series in 26 parts
Narrator
David Attenborough
9: Trespassers Will Be Sung At!
Territorial male song-birds chase away intruding strangers, yet tolerate neighbours. How do they know which bird is which? Bruce Falls of the University of Toronto; John Krebs of Oxford University: Donald Kroodsma of the University of Massachusetts at
Amherst; and Peter Marler of Rockefeller University. New York. reveal how bird song may function in territorial proclamation.
Producer MICHAEL BRIGHT BBC Bristol