By comparing the sugar-indifferent and sugar-responding receptor sequences, they identified the modifications enabling sweet perception. In addition to the timing of the sensory change, the researchers were able to uncover its molecular basis. 'We were very surprised by this result. Sweet perception emerged very early within the songbird radiation and then persisted even in species that do not rely primarily on sugary food,' says Baldwin. It turned out that the early ancestors of songbirds evolved the ability to sense sugar, even before they radiated out of Australia and spread across the planet. To identify the origin of this ability, the researchers reconstructed ancestral umami receptors at different locations on the songbird family tree.

Toda and Baldwin dug deeper and found that the umami receptors of nectar specialist honeyeaters, as well as those of other songbirds with varying diets, also respond to sugar. Indeed, their behavioral experiments showed that both a nectar specialist as well as a grain-eating songbird preferred sugar water to normal water. 'This was the first hint that we should concentrate on a range of songbirds, not only the nectar-specialized ones, when searching for the origins of avian sweet taste,' explains Baldwin. However, Baldwin and colleagues found an above-average number of other songbird species across the entire radiation that occasionally consume nectar or fruit. Certain songbird lineages, such as sunbirds, sugarbirds, and honeycreepers, are known to regularly consume large quantities of nectar. Nectar in the dietįootage of a New Holland honeyeater ( Phylidonyris novaehollandiae) drinking nectar from flowers outside Deakin University, Australia (slowed for viewing).įirst, the researchers systematically studied the diets of birds. The only known exception are the hummingbirds, who re-purposed their umami taste receptor to recognize carbohydrates.īut are all other birds unable to taste sugars? An international team led by evolutionary biologist Maude Baldwin of the Max Planck Institute for Ornithology in Germany and Yasuka Toda from Meiji University in Japan investigated this question. Birds, however, descend from carnivorous dinosaurs and lack an essential subunit of this receptor - presumably leaving most unable to detect sugar. It is well known that the sweet taste receptor is widespread among mammals. The rest of the animal kingdom is no different, as taste reliably helps to distinguish what is nutritious from what is poisonous. The sense of taste has an enormous influence on our diet - what we think tastes good often ends up on our plates. © Roy Burgess (Macaulay Library 290064381)īitter, salty, sweet, sour and umami are the five basic tastes that we humans perceive.

Songbird by Lisa Edward