During the wet season, metallic starlings – which have bright red eyes and a blue-green sheen – migrate from New Guinea to breed in Australian rainforests. As many as 1,000 of the raucous birds may descend on a single poison-dart tree to nest.
Amazing as this is, new research in PLOS ONE shows that these breeding colonies are even more incredible than we knew: the huge concentrations of starlings in poison-dart trees attract huge numbers of other animals, creating wildlife hot spots in a landscape with poor soils and low productivity. This is the first description of this spectacular system.
“You can see so many incredible animals at one time and place, and spectacular predator-prey interactions,” says lead author Daniel Natusch of the University of Sydney, Australia. The colonies are exceptionally noisy with starling chatter by day and are quiet at night. But the ground beneath the trees is busy with a diversity of wildlife around the clock.
Daytime animals from dingoes to bandicoots feast on the bounty of fallen seeds, starling eggs and nestlings, and guano-fertilized roots and seedlings. Darkness brings toads, pythons and other snakes, which swallow birds that fall out of the trees. Snakes also try – but often fail – to climb the trees to get birds in their nests. “Snakes thud to the ground beside you when they fall from the steep, smooth, trunk of the tree,” Natusch says, explaining that the starlings choose trees that are hard for snakes to climb.
The researchers discovered that many of the animals thronging these nest trees are 100 to 1,000 times more abundant than they are under trees without nests. These wildlife hot spots are also tiny at roughly 140 square meters, making them likely among the most dense and diverse aggregations of animals in the world.
Besides being disproportionately important for conserving native species, these hot spots attract enormous numbers of feral pigs and cane toads, which are not native. This presents an opportunity for controlling these introduced, invasive species. “The sites could be trapped for pigs or targeted by hunters,” Natusch says. “And large numbers of cane toads could be collected from them.”
Research Article: Natusch DJD, Lyons JA, Brown G, Shine R (2016) Communally Nesting Migratory Birds Create Ecological Hot-Spots in Tropical Australia. PLoS ONE 11(10): e0162651. doi:10.1371/journal.pone.0162651
Image Credit: Natusch et al (2016)