I love those photos of someone’s dog having a good shake after a swim, water spraying everywhere. But I had never seen a bird shake, until last week. It rained overnight, and in the morning up flew a hummingbird, perched on a twig, and:
Successfully blow-dried, she settled her feathers:
It turns out that until recently birds were known to shake after a bath, but not after rain. In 2011, The Royal Society published a magnificent paper analyzing the kinetics of the Anna Hummingbird’s shake. Here is a diagram that will give you a flavor of their work:
(From Ortega-Jimenez, V., and Dudley, R 2011. Aerial shaking performance of wet Anna’s hummingbirds.)
Astonishingly, they can shake while flying, not just while perching. And while perching they put their wings out to counter-balance the head angle, just as you can see in the first photo. The shake is super fast: 30 shakes/second. This is because the tinier the animal the faster it has to shake to get rid of the water. A dog shakes at 4-5Hz, but a mouse shakes at 27Hz.
Eyes on the Wild 
I enjoy watching the local birds shake after splashing in our bird bath here in Bristol, but had no idea some birds shake after rain. Imagine particularly important for hummingbirds as even tiny extra water weight could affect their vibratory movement.
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