Bird perch helps plants have better sex

A South African plant has evolved a special perch that encourages birds to help flowers reproduce with a partner, scientists have found.

Spencer Barrett, a University of Toronto researcher who co-authored the study, said scientists first became interested in the plant called Babiana ringens — a member of the Iris family — because it has tubular red flowers, suggesting that it was pollinated by birds. But strangely, it grows the flowers on the ground.

Many birds don't like to forage on the ground, Barrett told CBC's As It Happens, because that makes them vulnerable to predators. And while North America's hummingbirds can hover, no nectar-sipping birds in Africa have that ability and must perch when they visit a flower.

"Then when we looked at the plant carefully, we noticed there was this very odd structure," Barrett said. "It actually looks like a fattened version of the tail of rat."

The researchers noticed that when nectar-sipping sunbirds visit the plant, they grab onto that "rat tail," "turn upside down, then probe the ground-level flowers," Barrett said.

He and his colleagues decided to see what would happen if they cut the structure off.

"Basically, the birds were not very happy about losing their perch and only a small number visited the flowers on the ground," he recalled.

When the birds probed the flowers from the ground, it caused them to self-pollinate. That meant any offspring that resulted would have the same parent as both their father and their mother, instead of two different plants.

The researchers found that when the perch was there, the plants underwent more cross-pollination, produced more seeds and had higher quality offspring.

"What the perch does is position the bird in a manner that facilitates cross-pollination," Barrett said.

The researchers' findings will be published early next year in a special issue of the Annals of Botany.