[R]esearchers … put nearly 1,000 Peruvian hummers through lifting trials and flight tests over a two-year stretch in order to find out how their flying abilities are affected by the lower oxygen and thin air of higher elevations.
The results, which appeared this week in the Proceedings of the National Academy of Sciences (PNAS) Online Early Edition, show a clear decline in hummingbirds’ lifting ability with altitude, not unlike that seen in athletes competing at high elevations.
What this means for hummingbirds is less reserve power for the bursts of flight needed to chase off competitors or escape from predators, said researchers from the University of California, Berkeley, and the California Institute of Technology.
Scientists have long been fascinated with how hummingbirds — one of Earth’s smallest, warm-blooded vertebrates — can nutritionally maintain their high-metabolic daily lifestyles, let alone fly thousands of miles during migration.
University of Arizona ecologist Todd J. McWhorter has examined a less-studied facet of these amazing creatures — their ability to consume several times their body mass in water every day. Humans, rats, domestic pigeons and gray parrots would succumb to ‘polydipsia,’ or water intoxication, before they could drink amounts of water anywhere near their own body mass.