Berkeley Biologists Discover Sunbirds Use Unique Tongue Suction to Slurp Nectar Unlike Hummingbirds

New UC Berkeley research reveals sunbirds use a novel tongue suctioning technique to drink nectar, a major departure from hummingbird feeding habits.

By: AXL Media

Published: Apr 14, 2026, 7:32 AM EDT

Source: Information for this report was sourced from EurekAlert

A Breakthrough in Avian Biomechanics

Researchers at the University of California, Berkeley have identified a novel feeding mechanism in sunbirds that fundamentally differs from other nectar-eating birds. While hummingbirds are known to sponge up liquid and wring it into their mouths, sunbirds actually suction nectar through their tongues. Published in Current Biology, the study confirms that sunbirds are the first vertebrates discovered to use their tongues to create the negative pressure necessary for slurping. According to Rauri Bowie, a professor of integrative biology at UC Berkeley, this finding represents a remarkable example of nature developing different solutions to the same ecological challenge.

The Failure of the Capillary Action Theory

For years, biologists operated under the assumption that nectarivores relied on capillary action, a passive process where surface tension pulls liquid into tubular beaks. However, experts doubted this theory because the process is too slow to fuel the high-energy lifestyles of birds like sunbirds and hummingbirds. According to David Cuban, the study’s lead author and a postdoctoral fellow at Brown University, early high-speed video evidence showed air bubbles around sunbird tongues that would have disrupted capillary action. This prompted a deeper investigation into how these birds achieve the rapid calorie intake required for their active displays.

Anatomy of a Hermetic Seal

To uncover the mechanics of this suction, the research team conducted experiments in Africa and Indonesia using high-speed cameras and 3D-printed artificial flowers. They discovered that sunbird tongues possess a V-shaped trough at the base and specialized flexible flaps. As the bird inserts its tongue into a flower, it presses the base against the upper beak to create an air-tight, hermetic seal. When the tongue is pulled back, it generates the negative pressure required to draw nectar through the tongue's groove. Anatomical confirmation was provided via microCT scans conducted at the Museum of Vertebrate Zoology.