Hummingbirds evolved a strange taste for sugar
Nectar-sipping birds seem to have regained a sweet tooth lost by an ancestor
Hummingbirds are drawn to nectar in an unusual way. Instead of depending on a sugar sensor found in many vertebrates, the flitting, frenetic birds use a repurposed sensor that normally responds to savory flavors, scientists report in the Aug. 22 Science.
Researchers led by Maude Baldwin of Harvard University and Yasuka Toda of University of Tokyo studied the genomes of 10 bird species and found no hint of the gene that encodes the sweet detector that most vertebrates rely on. Like those birds, hummingbirds probably also lack the gene, the researchers reasoned. But experiments on cells in dishes revealed that hummingbirds’ umami receptors, which normally detect savory amino acids, pick up the slack and detect sucrose, glucose and fructose.