From Britain on Film, available on BFI Player

From the BFI website:

A visual aid for children to learn about natural history, this film follows two children, Rachel and Nigel, who accompany keeper Harry Barnes through a Fenland mere to discover the birdlife and wildlife that lives there. The children travel in a punt along a stretch of water and peer through the reeds looking at coots, a swan with cygnets, and a nesting Great Crested Grebe. They see moorhens, a reed warbler and a whitethroat warbler, toads and ducklings.

The East Anglian Film Archive, the first and largest Regional Film Archive in England, was established in 1976. Since 1984, EAFA has been owned and operated by the University of East Anglia, Norwich (UEA), to support research and work to preserve our moving image heritage. More than 250 hours are freely available online as examples of the wide range of film which attracts interest the world over.