Most people know hummingbirds are tiny, cute and fun to watch. What they may not realize is that they are smart, too.
Rufous hummingbird (Selasphorus rufus) feeding on an artificial flower at the University of … [+]
Andrew Hurly
Scientists from the University of St. Andrews found evidence suggesting hummingbirds keep track of where flowers are located using basic math.
For the study, feeders with sugar water in them were placed in the territory of nine wild hummingbirds. After the birds learned to drink from the feeders, researchers replaced them with ten identical feeders in a line. Only one of those feeders contained sugar water. The rest were empty.
Once the birds figured out which feeder held the sugar water, the researchers moved the feeders to a new location and changed the distance between the feeders. This was to prevent the birds from using landmarks or relative distance to find the right feeder. The same feeder in line, for example feeder number two, still held the food. Birds went to the right feeder most of the time through four different rounds of testing. The researchers concluded that the birds were able to keep track of the order that the correct feeder appeared in the line.
These results were published in Proceedings of the Royal Society B.
Maria Tello-Ramos, the lead author on the paper, said the study falls short of showing that the birds can “count.” In true counting, each number in a set is tagged as in “one”, “two”, “three.” For this study, the birds needed to know how many empty feeders were on either side of the feeder with food, but they didn’t necessarily need to count each one individually.
Tello-Ramos said hummingbirds make good study animals because they have to feed so often. Chimpanzees might only want food every hour, but hummingbirds eat every ten minutes. This meant each bird could be trained and tested within half a day. The whole study only took four days.
Numbers aren’t the only way that hummingbirds forage. Tello-Ramos said they also use color cues and landmarks to find flowers.
She said it is always interesting to learn that animals can do basic math like remembering a sequence of objects given that so many people struggle learning math in school. Since hummingbirds are pollinators, they have a lot of ecological importance and are important animals to understand, she said.
Mary Caswell Stoddard, an assistant professor at Princeton University, said in an email that the discovery that hummingbirds have a sense of numerical order provides a richer picture of how hummingbirds have evolved to synthesize all kinds of information—color, spatial location, sequence—when searching for food.
“Hummingbirds are nimble learners,” said Stoddard, whose lab conducts work on color vision in wild Broad-tailed Hummingbirds. “These experiments, performed in the wild, show us how hummingbirds really behave in their natural habitats—and that’s key.”
Alejandro Rico-Guevara, an assistant professor at the University of Washington studying hummingbirds, said he wasn’t surprised by the paper’s results since previous work has shown that bumblebees, which have much smaller brains, can figure out the position of items in a series of food rewards. But he said the new study shows for the first time that vertebrate nectarivores can use the order of flowers while foraging.
Having the ability to track the order of flowers would be useful to hummingbirds when they don’t have other available information like landmarks, said Rico-Guevara. Since hummingbirds use a lot of energy hovering, it is important that they know where certain flowers are, when the nectar in the flowers will refill after a feeding and how to get there before other birds drain the flowers.
Correcting for size, birds have more neurons in their brains than primates, said Rico-Guevara. Hummingbird brains make up about 4.2% of their total body weight on average. In humans, that figure is only about 2%.
“So if someone calls me “birdbrain,” or even better “humming-birdbrain,” I’ll take it as a compliment,” he said.
