May 4, 2005—Scientists say that they've proved that the tall erect spike grown by the South African plant Babiana ringens has a single purpose: It is a perch for birds, making it easier for them to drink nectar from the plant's peculiar ground-level flowers.

The perch allows the malachite sunbird, the plant's main pollinator, to insert its curved beak into the flowers from above. When a bird assumes the upside-down position, its breast is brushed with pollen. The bird then spreads the pollen to other B. ringens (commonly known as rat's tails), thereby cross-pollinating the plant species.

Reporting in tomorrow's issue of the science journal Nature, researchers said that when they removed the perch, it decreased the mating success of the plant because significantly fewer sunbirds came to drink nectar. Male sunbirds were particularly less inclined to visit a plant that did not have a perch, possibly because they have much longer tail feathers, which could interfere with ground landings and takeoffs.

The research was done by Spencer C. H. Barrett of the University of Toronto, Canada, and Bruce Anderson of the University of KwaZulu-Natal, Scottsville, South Africa.

—David Braun

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