The Swift Parrot is a Tasmanian bird endangered by logging and collisions with windows and fences. It turns out, however the biggest threat is one of the few animals even cuter than itself, the sugar glider.
Australia has such a surplus of charismatic animals it can be hard to gain an international profile, and the Swift Parrot's (Lathamus discolor) name is not well known outside its habitat range of south-eastern Australia. The only member of its genus, the bird breeds in Tasmania in the southern spring before migrating to the mainland in autumn.
Only 1000 breeding pairs are thought to exist and it is listed as endangered by the International Union for the Conservation of Nature. Although its habitat on the mainland has been more heavily cleared than in Tasmania, it is in the island state that its problems are greatest. Not only does it require old tree hollows for nesting, but there were fewer suitable habitats to start off with.
When looking for the proximate cause of the parrot's demise sugar gliders may not be the most obvious suspect. The glider (Petaurus breviceps) looks too gorgeous to be a threat to anything other than honey or flowers. The fact that it's scientific name translates as “short-headed rope-dancer” only adds to this impression, but the glider is omnivorous, and its diet extends not just to parrot eggs, but to fully grown female parrots at a pinch.
Although their habitat extends from New Guinea to the southern tip of the Australian mainland, Tasmania during the Ice Age may have been too cold for the gliders, as they were not found there until introduced in 1835, where they have become the parrot's only predator.
The fact that gliders prey on parrots was not known until a team from the Australian National University revealed it in Diversity and Distributions. The discovery explains a lot about the bird's decline.
“That predation was so severe that, on average across mainland Tasmania, only 17% of swift parrot nests were actually successful and all of those failures were as a result of sugar gliders eating the swift parrot, either the females or their eggs or both," lead author Dr Dejan Stojanovic told the ABC.
However, the story is not as simple as a case of an invasive species running (or in this case gliding) amock to the detriment of a species that has not evolved defenses. Logging of old growth forest has always been the main suspect in the parrots decline, and it seems it may still be responsible – in areas where logging has occurred the glider is far more likely to eat the parrot's eggs, either as a result of loss of other foods or because the parrot has to choose more vulnerable nesting sites.
There are also concerns the glider may be threatening the even more endangered orange bellied parrot (Neophema chrysogaster). Once famously denounced by the then Premier of Victoria as a “trumped up corella”, the 50 surviving wild orange bellied parrots are among the most endangered birds in the world.
Stojanovic previously revealed that the parrot likes tree “cavities with small entrances, deep chambers and wide floors”, the first presumably to keep gliders out. Such cavities are restricted to large trees, whose numbers are particularly threatened by logging.
The newly elected Tasmanian government has promised to rip up an agreement designed to protect the state's high conservation value forests.