# Hummingbirds Can Shake Their Heads at 34g!

Most birds aren’t very active in the rain. They can fly in the rain if they have to, but they prefer not to. After all, the longer they are in the rain, the soggier they get. This adds to their weight, meaning they have to work harder to generate the lift necessary to stay in the air. So in general, birds tend to wait out the rain. Like most rules in biology, however, this one has an exception. The activity of hummingbirds is not significantly affected by most rainfall.1

How these incredible birds can fly even after being in the rain a long time was a bit of a mystery to scientists, but thanks to some artificial rain and high-speed photography, we now know that hummingbirds regularly dry themselves off by shaking like a dog.2 The shaking propels the water off their feathers so that the tiny birds don’t get too waterlogged. If you watch the video above (which comes from the referenced study), you can’t help but be reminded of a wet dog coming in out of the rain. Of course, the dog isn’t flying at the time, but the similarity is remarkable.

There are (at least) two amazing things about this. First, as the video shows, the birds can do this while they are still in flight! It clearly affects the flight trajectory, but the bird manages to stay in the air the whole time and then recover to its planned flight path once it is dry. I can’t begin to imagine how the bird manages to stay in flight while it is doing this or how it can know where it is well enough to immediately adjust its flight path to compensate for the change that the shaking induced.

The other amazing part of this study is the acceleration the authors report. According to their measurements, when a hummingbird shakes its head to dry off, the head accelerates at up to 34 times the acceleration due to gravity! In other words, the head pulls off 34g’s of acceleration. To put this in perspective, a Ferrrari 333 SP accelerates from rest at 0.75g, and a fighter pilot might experience as much as 9g’s in a tight maneuver.3 Compared to how a hummingbird shakes its head to dry it off, 9g’s isn’t even warming up! To top it all off, this amazing acceleration occurs in a body that most people would describe as “delicate!”

The more I study God’s creation, the more amazed I become.

## REFERENCES

1. Dan True, Hummingbirds of North America: Attracting, Feeding, and Photographing, University of New Mexico Press, 1995, p. 56

2. Victor Manuel Ortega-Jimenez and Robert Dudley, Aerial shaking performance of wet Anna’s hummingbirds,” Journal of the Royal Society Interface doi:10.1098/â€‹rsif.2011.0608, 2011.

3. Richard A. Muller, Physics for Future Presidents: The Science Behind the Headlines, W. W. Norton & Company, 2009, p. 212