Welcome to the newest edition of The Why. “Why do hummingbirds love sweets?” you ask? Good question . . . and timely as well. (It sure beats answering the question: “Why does hot sauce sting when you get it in your underwear?”)
Hummingbirds, unlike humans—well, non-vegan humans, at any rate—eat insects for their fat and protein. Oddly, most of a hummingbird’s diet is made up of sugary nectar. Hummingbirds, however, should not be able to recognize sweets.
According to a team of international biologists, people and some other creatures who like sweets have a couple of sensory receptors named TIR2 and TIR3. Experts note, however, that hummingbirds don’t have TIR2 sensory receptors. So how do hummingbirds even know that sugar water and nectar are sweet in the first place?
Researchers believe that over millions of years a receptor that used to help hummingbird ancestors detect the savory umami taste was converted by genetic mutation into a receptor for sweets. Their study, published recently in the journal Science, reports that they did a number of experiments having to do with the gene for TIR3.
They also identified 19 mutations that made it possible for the taste receptor to recognize sweets. There may even be other mutations — in the TIR3 gene as well as the previously-mentioned TIR1 gene — that aid in making hummingbirds specifically sensitive to sweet tastes.
The scientists went into the Santa Monica Mountains among other places to conduct their field tests. Hummingbirds only required three licks to establish if a test feeder had a sweetened solution or just water. Researchers stated that hummingbirds were clearly not happy with the plain water and after tasting it they “often displayed a characteristic behavioral pattern involving beak withdrawal, head shaking, and/or spitting.”
On the other hand, the hummingbirds seemed clearly pleased to drink from the feeder with sweetened liquid. They enjoyed solutions made with sugar, fructose and glucose. They also drank solutions made with the sugar alcohols erythritol. They spat out any solutions made with artificial sweeteners acesulfame potassium (Sunett and Sweet One), aspertame (NutraSweet), cyclamate and sucralose (Splenda).
Finally, the investigative team was able to establish that the mutations that changed TIR3 into a sweet detector had to happen over the past “42 million to 72 million years” thus permitting hummingbirds to slowly transform into a distinct group of nectar-drinking birds. Therefore they love sweets because mutations have given them the capability to do so.
Why do hummingbirds love sweets? Now you know.
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