The Passenger Pigeon was once the most numerous species of bird on the planet. These birds would form enormous dense flocks on seasonal migrations that would take hours and sometimes days to pass overhead. But this made them an easy target – a single shot would bring down 30-40 birds. Large-scale commercial hunting commenced in the early 1800s to provide cheap meat for growing cities in the eastern United States. The industry grew with the spread of the railroads. The pressure to kill more birds prompted the development of the forerunner to the machine gun. In one year in Michigan alone, a billion birds were slaughtered.

Eventually the vast flocks couldn’t withstand the hunting pressure. From an estimated population size of still billions in 1800, they were hunted to a level of several thousand by the 1880s. The last wild bird was captured in 1900. Attempts to re-establish the species through captive breeding failed – it was a gregarious bird that needed large numbers for breeding but these large numbers no longer existed. The last known passenger pigeon (named "Martha") died at the Cincinnati Zoo on 1 September 1914.

Another story of a surprising extinction event involves the Rocky Mountain Locust. When these insects swarmed, they would darken the skies for days. One swarm described in 1875 was almost 3000km long and 180km wide – and the air was filled with a sound like a thousand scissors. Crop losses were enormous. Many families gave up farming and fled to the cities. Even blankets protecting kitchen gardens were devoured, along with the vegetables. This species of locust was considered the greatest threat to agriculture in the west. Then, suddenly, numbers dropped. The last live specimen was found on the Canadian prairie in 1902. It wasn’t named "Martha" and, unlike the Passenger Pigeon, no one mourned the loss.

It’s demise – at a time before DDT was invented and before Plague Locust Commissions could dream of aerial spraying with insecticide – was a mystery until the 1990s. Maps of the locusts’ range each year in the 1870s were re-discovered and studied. Every summer, regardless of whether the locusts were swarming, mating adults could be found in a limited area in the river valleys of Montana and Wyoming, where they buried their eggs along the banks of streams. By 1880, this limited area had been settled and was under cultivation. These settlers modified the locusts’ habitat by ploughing and irrigation. They had, unknowingly, stopped the reproduction and killed off the species.

These stories could be repeated for the Grey-Headed Flying Fox sometime in the near future. Yes, they are still numerous but there are less than a third of what was estimated to have been here 200 years ago. Like the Passenger Pigeon, they roost in large colonies and only produce one young per year. Like the Rocky Mountain Locust, breeding sites occur in areas favoured by humans for other uses. A key habitat is the diminishing rainforest on the floodplains of the Clarence River. This habitat itself is under threat (it is an endangered ecological community). Susan Island is an important site but, as use of this site concentrates due to losses elsewhere, it is under increasing pressure. The area of lowland rainforest needs to be increased.

But there are broader implications for a species decline. Flying Foxes are the key pollinators of eucalypts. Without them, our forests will decline. And that would be a sorry tale.

-Janet