From the field

The energetic edge of existence

How do hummingbirds perform their Olympian feats?

Kenneth Welch

When hovering, the ruby-throated hummingbird beats its wings more than 50 times per second. (Photo by Michaela Sagatova)

While conducting my PhD thesis, I spent several summers working before dawn on a subalpine meadow at the Valentine Easter Sierra Reserve (VESR). Despite the overwhelming beauty of the locale—a field research facility managed by the University of California, just south of Yosemite National Park—it was the living gems flitting around those meadows that captured my undivided attention. I’ve been lucky enough to study hummingbirds, some of the most elite athletes of the natural world.

Hummingbirds make flight look effortless. Yet, these tiny birds expend a staggering amount of energy while hovering, flapping their wings 50 times or more per second. Gram per gram, the hovering hummingbird consumes energy at a rate more than 10 times that expended by an Olympic marathon runner.

Each fall, every hummingbird in Ontario must also migrate to Mexico. Our local ruby-throated hummingbird travels more than 4,000 kilometres south, embarking on a series of uninterrupted flights of several hundred kilometres each. Between each leg of the journey, the birds rebuild muscle and store fat at a mind-boggling rate, gaining more than 50 percent of their body weight in just a few days.

For an animal that seems to live each day at the energetic edge of existence, this is an incredible feat. And the mechanism by which this bird accomplishes it is still poorly understood. Lab-based studies allow us to quantify the cost of flight and the bird’s rate of nectar intake. The controlled setting of a lab, however, doesn’t allow us to examine just what effects a dynamic, variable environment might have on energy balance and fat storage.

I maintain a series of specially outfitted feeder stations at the Koffler Scientific Reserve (KSR), an internationally recognized U of T research site north of Toronto. These stations automatically record the weights of dozens of hummingbirds each time they visit, allowing us to track survival and monitor energy reserves in relation to weather conditions, flower availability and competition in real time. By studying these amazing birds in their natural environments, my research team at UTSC hopes to better understand how hummingbirds prepare for migration and what effect climate change might have on their future distribution and abundance.

An invaluable resource, KSR supports research and education that benefit dozens of professors, post-doctoral fellows and graduate students, as well as hundreds of undergraduates and members of the public from across the GTA and around the world. In light of recent announcements that important federally funded research stations, such as the Experimental Lakes Area in Northern Ontario, are soon to close, the continued existence of university-supported facilities like KSR and VESR is increasingly critical. Research stations remain indispensible as outdoor laboratories fostering scientific advances that help us understand as well as appreciate the natural beauty that surrounds us.

Kenneth Welch is an assistant professor of biological sciences at UTSC.