It sounds like something out of a horror story, but in Puerto Rico there is a species of tree that traps and kill baby birds, and then feeds on the bird’s nutrients.
Pisonia trees or “bird catching” trees are proof that nature is freakily cruel. From branches can be seen mummified bodies of bird lured by the killer trees and at the bottom of the trees the ground is covered in the carcasses and bones of dead birds.
These killer trees attract their prey in an ingenious way. They produce small sticky fruits that are covered in hundreds of tiny hooks. These get stuck to the birds who feast on them and if enough get stuck on them they can get stuck on the tree where they slowly starve and die or fall the ground when they try to fly.
But it turns out that these trees are not deliberately killing the birds, it’s an unintended consequence of their desire to spread their species. As Alan Burger, an ecologist at the University of Victoria, who has studied the trees for over 20 years, explains,
“The results from my experiments showed quite convincingly that the Pisonia derived no obvious benefit from fatally entangling birds,” says Burger.
Instead, Burger discovered that the extreme stickiness of the seeds was to ensure that they would remain stuck to sea birds, who regularly feast on the trees fruits By continuing to stick to the birds feathers for up to 4 weeks rather than be washed off immediately by the sea, the seeds can be transported much longer distances. Allowing the trees to colonise greater expanses of land and enhance the survival of their species.
“Having the birds alive seems to be the key to dispersal, but an unfortunate consequence of having extremely sticky seeds, and producing many seeds in a cluster, is that some birds get fatally entangled,” Burger says.
So these bird killing trees aren’t committing murder, its more like manslaughter, or should that be birdslaughter?!