The Avians are a sapient species of flightless bird-like beings which possess feathers, beaks and claws. They inhabit a world covered in vast rainforests, and build their cities in the canopies. Their language consists of a mix of songs and visual displays.
This species has evolved a form of symbiosis with the trees they live in, which provide naturally-formed nests for the females to lay their eggs in. The chick's droppings also combine with the fruit juices to create a substance known as the Yolk of Darts, which is harmless to females and chicks but poisonous to the males. This helps to prevent the most aggressive males from destroying the eggs of their rivals.
Most notably, the Avian society operates on a harsh juridical system in which the punishment for any crime is applied not to the criminal directly, but to the person most dear to the criminal.
- Big Finish Doctor Who audio stories - "Circular Time" (2007)