Whistler is a heron who appears in the books and the TV series. He joins the group of Farthing Wood animals during their journey to White Deer Park after meeting them at a quarry. His name derives from a hole in his wing from an old gunshot wound, which makes a whistling noise as the air passes through it when he flies.
Whistler has a very helpful nature, collecting fish for the other animals and saving Toad from a carp before he has even joined the group. He proves to be a very useful member of the group, carrying the smaller animals across the motorway, catching fish to keep his friends alive during the first winter in White Deer Park and eating a vast amount of rats when they try to take over the park.