Hummingbirds have long intrigued scientists. Their wings can beat 80 times a second. Their hearts can beat more than 1,000 times a minute. They live on nectar and can pack on 40 percent of their body weight in fat for migration.
But sometimes they are so lean that they live close to caloric bankruptcy. At such times, some hummingbirds could starve to death while they sleep because they’re not getting to eat every half-hour or so. Instead, they enter a state of torpor, with heartbeat and body temperature turned way down to diminish the need for food.
Kenneth C. Welch Jr. at the University of Toronto, Scarborough has studied the metabolisms of hummingbirds for more than a decade. His most recent research with Derrick J.E. Groom, in his lab, and other colleagues is on the size and energy efficiency in hummingbirds. By using data on oxygen consumption and wing beats to get an idea of how much energy hummingbirds take in and how much work they put out, the scientists found that during strenuous hovering flight, bigger hummingbirds are more efficient energy users than smaller ones. The research was published in Proceedings of the Royal Society B.
Excerpts from a telephone conversation with Welch have been edited for clarity and length.