By Nicholas St. Fleur
Hummingbirds are the acrobats of the avian family—flapping their wings more than 45 times a second, they hover forward, backward, and even upside down. But their mid-air moves are energy exhaustive, and they must feast on nectar at least once a day, even in severe weather, or they will perish. So when a storm rolls in, how does this tiny bird fare when being pummeled by heavy rain drops that can collectively feel like 38% of its body weight? Quite well, according to a study published online today in the Proceedings of the Royal Society B. Similar to experiments conducted on mosquitoes earlier this summer, researchers subjected five male Anna's hummingbirds (Calypte anna) to light, moderate, and heavy rain conditions in the lab, and then analyzed their flight responses with high-speed video (seen above). They found that the birds were barely affected by light and moderate rain, but that they had to take on a completely different body posture to maintain aerial control under heavy rain, shifting their bodies and tails horizontally, beating their wings faster, and reducing their wings' angle of motion. The researchers found the position change paradoxical at first because each bird exposed more of its back to the incoming rain. But further investigation revealed that this position may reduce the amount of drops hitting the bird's wings, which helps keep it more stable in the air. The researchers also found that the hummingbird's water-resistant feathers absorbed 50% of the impact from the heavy falling drops, helping the animal stay light in flight, and in control no matter the weather.
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