Hummingbirds can count? Yes, researchers have discovered that rufous hummingbirds can count their way to food supplies. Maybe we should call them homing-birds.
Many cottagers will have noticed an unusual springtime occurrence: hummingbirds hovering around the area where the sugar-water feeder usually hangs, even before the owners have put it back out for the season.
“Hummingbirds are really good at remembering location,” says Andrew Hurly, a biology professor at the University of Lethbridge in Alberta. He and a team of researchers from the University of St. Andrews in Scotland recently published a report in the Proceedings of the Royal Society B showing that rufous hummingbirds are not only able to remember the locations, they’re able to count their way to a particularly bountiful flower.
In late spring 2017, the researchers arranged a test in the Westcastle Valley in the Alberta Rockies. They first set up artificial feeders at various locations around the valley to attract territorial male hummingbirds, nine of which they trapped and marked with non-toxic ink for later identification.
Next, they set up a linear array of 10 identical artificial flowers, spaced evenly apart. One flower was filled with a 25 per cent sucrose solution, while the other nine were empty.
Each of the birds would eventually find the treat-bearing flower, feed, and then fly away. But, given their extremely high metabolisms—hummingbirds beat their wings up to 70 times per second and their hearts beat more than 1,000 times per minute—they feed frequently. So, 10 or 15 minutes after their first feeding, they would come back to the array and most of the time would first return to the flower with the food in it. After each bird had visited the feeder four times, the researchers would switch it with one of the other feeders. “We were sitting about 10 metres away on lawn chairs,” says Hurly of their in-the-field observations.
At first, the birds would go to the feeder that initially had the food it in. But they quickly learned which one offered a reward, and 50 to 60 per cent of the time they would return to that one first, until it was moved again.
“At least one of the things the birds learned was the order [the feeders were in]. That’s a skill very close to counting,” says Hurly.
The rufous hummingbird is one of the smallest birds found in Canada, only 7 to 9 cm long and weighing between 2 and 5 grams. Yet they migrate thousands of kilometres from their wintering grounds in Mexico to breeding grounds in Alberta, British Columbia, and as far north as Alaska.
“We think they’re using landmarks” to migrate, says Hurly. Initially, those landmarks are large-scale—bird’s-eye view if you will—and then they get progressively more localized as the birds near their favoured feeding and breeding grounds, kind of like how we zoom in on Google Maps. Now we know they’re also likely counting off landmarks along the way. (“Hey kids, we’re about to pass the Big Chute Marine Railway. We’re almost there!”)
One final note about those cottage hummingbird feeders. “A bright red hummingbird feeder will attract them the first time. But, after that, they don’t need [the brightly coloured container],” says Hurly, given that they will remember its location. And while there’s no research that says adding red colouring to the sugar water is safe for hummingbirds, at the very least it’s a waste of money and effort. “I would argue against using food colouring,” says Hurly.