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Hummingbirds Evolved a Sweet-Tooth to Better Enjoy Nectar

Aug 21, 2014 03:33 PM EDT
Humming birds may have specifically evolved just to taste sweet nectar, as most other birds are only capable of tasting savory foods.
(Photo : Flickr: Gszrir)

Imagine being a hummingbird. You can flap your wings at incredible speeds, make precision turns and hover in the air like nothing else on Earth. You are a master of flight and spend every day enjoying the great outdoors, sniffing beautiful flowers and drinking sweet-sweet nectar.

But there's something wrong.

You can't actually taste the sweetness of the nectar guzzle because traditional avian taste buds don't account for it. How unfair is that? Suddenly being a hummingbird doesn't seem so great.

So what do you do? You evolve.

That, at least, is what researchers claim the earliest of hummingbirds did, according to a study recently published in the journal Science.

On the surface of animal taste buds, there are receptors known as T1Rs. These receptors bind to molecules in certain foods to trigger a neurological response. In humans, for instance, T1R2 and T1R3 work together to deliver the "sweet" taste we get from sugars.

However, it turns out that birds don't have the adequate genetic information that codes for T1R2 formation, meaning that they can only taste savory foods, which is detected with T1R1. Yet hummingbirds have still previously shown that they prefer sweet nectar over other sustenance. So how can they tell the difference?

Maude Baldwin, of Harvard University, and her colleagues determined that hummingbirds have repurposed T1R1 and T1R3 on a very basic level so that they can detect sweet in place of savory.

According to Baldwin's study, there is clear evidence that proteins on the surface of the two receptors have undergone a very specific modification that is not seen in other birds. It is suspected this modification enables the detection of sweetness.

"The change in the taste receptor was certainly not the only factor or aspect of hummingbird biology that was important [for them to feed on nectar], but it seems like it played an important role," Baldwin told New Scientist. "There are many behavioral and physiological changes that have occurred between hummingbirds and their ancestors: small body size, a long bill and changes in the wing which allowed them to hover."

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