Tools of the Trade: Hummingbird Tongues

Among  the many reasons hummingbirds as a class are extraordinary is their tongues. Much of a hummingbird’s energy comes from drinking nectar. And the amazing tongue of the hummingbird plays a critical role in harvesting nectar from flowers. The precise role of the tongue wasn’t even discovered until 2011.

But before we get to that, let’s look at a hummingbird tongue. This is a Fawn-breasted Brilliant, about as average as a hummingbird can be.

Fawn-breasted Brilliant, Rio Silanche, Ecuador

But this Fawn-breasted Brilliant felt like sticking his tongue out, something that normally only happens inside a flower blossom.

Okay, Some Tongue

But that’s not even a fair start. After all, some of those flowers are very large.

Full Extension

You can see the tongue is about 2.5 times as long as the bill, which itself is pretty long. The first and most obvious question is where the hummingbird keeps that thing when it’s not sticking out. And the answer is that there is a structure, the hyoid apparatus, which is a forked structure made of a number of small bones and connected muscles, that wraps around the entire skull, coils around the eyes, and controls the tongue extension. The closest similar structure is found in woodpeckers.

For many years it was believed that the tongue functioned as a capillary tube, using surface tension of the nectar; high speed videography by Alejandro Rico-Guevara and Margaret A. Rubega has shown instead it works as a fluid trap. Here’s a schematic:

Close-up views of a hummingbird’s tongue. A tongue’s two forks uncurl in nectar (top), but curl back up to trap the sugary fluid when leaving it (bottom). Alejandro Rico Guevara/PNAS

There’s some good high speed videography of the tongue in action in a Wired article from a few years ago if you are curious and have the bandwidth.

It’s an astonishing adaptation. The tongue allows very speedy collection of high volumes of nectar, fueling the high energy behavior of the hummingbird. The whole business takes only a handful of milliseconds.

A hummingbird flying is amazing enough. But ornithologists are discovering that the flying skills are in many ways the least of the adaptations.