UNSW researchers Corey Callaghan, Shinichi Nakagawa and William Cornwell report the global population of 9 700 species of birds, (92 per cent or so of the total). Using citizen-science observations, they did the math to conclude there are 50 bn birds in the world.

This includes 10m Sulphur-Crested Cockatoos, most of which are on CMM’s deck.