Rufous hummingbirds use numerical order to figure out which flower in line is the juiciest.
Donald M. Jones/Minden Pictures
Tiny, feisty rufous hummingbirds are known for their long migrations, which take them up and down the length of North America each year. Now, they have a new claim to fame: They can keep track of particularly juicy flowers depending on where they appear—first, second, or even fourth—in a line-up of blooms. Although this understanding of “numerical order” may sound simple, it’s a complex skill that may help hummingbirds remember the easiest routes between nectar-rich flowers. It’s also the first time researchers have seen the ability in a wild vertebrate.
It’s a “really impressive” study says Stuart Watson, an animal cognition researcher at the University of Zürich who was not involved with the work.
Lots of animals can count, and some can understand how things fit together in a sequence. For example, rats, guppies, and monkeys trained in a lab can all use sequences to find food. But this doesn’t tell us whether—or how—wild animals might use that ability in a natural setting.
So Susan Healy, a biologist at the University of St. Andrews, and colleagues turned to rufous hummingbirds (Selasphorus rufus). The rust-colored males of the species, which weigh less than a nickel and are just 8 centimeters long, have…