Hummingbird Tongue Actually Acts as Micropump

Hummingbirds are not drinking nectar in the way we thought.

As tiny birds in a hurry, they're doing it the efficient way. A recent study found that a hummingbird's tongue acts as a micropump and does not involve capillary action, as scientists previously believed. Researchers Alejandro Rico-Guevara, Margaret Rubega, Tai-Hsi Fan from the University of Connecticut say that the elastic expansion of the bird's tongue grooves draws fluid into the beak.  

The research that they recently published in Proceedings of the Royal Society B puts into question fifty years of past research regarding how hummingbirds consume nectar from flowers.

"Our research shows how hummingbirds really drink and provides the first mathematical tools to accurately model their energy intake, which in turn informs our understanding of their foraging decisions and ecology," said Rico-Guevara in a statement.

The study explains that when nectar enters the hummingbird's bill, the bird compresses its tongue, which remains flattened until contacting the nectar surface. Then the bird's tongue reshapes in order to fill completely with nectar.

Researchers observed and measured free-living hummingbirds throughout seven countries using modified transparent feeders, which simulated nectar volumes and concentrations of hummingbird pollinated flowers. In total, 96 foraging cycles of 32 birds were observed. They were from 18 species, from seven out of nine of the hummingbird clades. 

The elasticity of the tongues' grooves allows nectar to fill at a higher rate than capillary-based models would allow. This comparison was discovered by accident when capillarity occurred once as one of the tongue groove tips adhered to the feeder before the nectar pool. Thanks to high-speed video, that moment was captured. Expansive filling took place in one groove, while capillarity took place in another, clearly demonstrating the significant difference between the two filling rates.

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