I get asked a lot “what do birds do when it rains?”.
My standard answer is that they go inside and watch their stories on the moving picture box. After a quizzical eye roll (or sometimes a blank stare), I’ll sometimes try to clarify things. But in doing so, we’ve got a couple things to address:
- Birds don’t live in nests. Nests are for reproduction. Outside of the breeding season, most birds just find a place to roost (perched on a branch somewhere).
- Birds, like mammals, are endotherms. They make their own body heat, which allows them to remain active when the environment is a lot colder than their body temperature.
- Feathers are great insulators. They trap warm air close to the body and so keep birds really well-protected. I wrote about this fact in another blog post somewhere awhile ago.
- Feathers are also good at repelling water, which is really important to their ability to be good insulators. But, feathers only work this way when they’re well-taken-care-of, which is why you often see birds preening. Now, in ducks and a lot of water birds, there is a gland (the uropygial gland). The secretions from this gland give the feathers of these birds an extra degree of protection from water.
But what about the cardinals and finches in my yard? And here’s what people are normally getting at. What happens to songbirds when it rains. Last week in Charlotte was a good time to see the various strategies that birds use. The rains went on for a long time, but the intensity changed dramatically. At times, they were strong and intense. Other times it was a light drizzle. And the birds? Well, they responded to these differences.
During the lighter rains, the cardinals, finches, wrens, towhees, and thrashers in my yard kept doing their things. Flying around, vocalizing, talking smack. Songbirds can do this without worry not because of the oils from the uropygial gland, but because of the physical structure of a feather. Feathers are very cool (and complicated) structures at the microscopic level. It’s not a solid thing, but a lot of very small barbs and hooks with tiny air holes between them. This structure actually helps make water bounce right off.
Bormashenko, E., Y. Bormashenko, T. Stein, G. Whyman, and E. Bormashenko. 2007. Why do pigeon feathers repel water? Hydrophobicity of penne, Cassie-Baxter wetting hypothesis and Cassie-Wenzel capillarity-induced wetting transition. Journal of Colloid and Interface Science. 311: 212-216,
Now, if you don’t want to dig into that article, don’t worry. It’s not really for bird people. It is however, for product designers. And that’s a separate little thought-let in my head. Birds do some pretty amazing things. We’re still figuring out how they solve problems like staying dry and we’re using that knowledge to change how we build our own new materials and structures. Cool, eh?
During the heavy rains, though, this mechanism doesn’t work as well. If their feathers get saturated or water gets under them to their skin, they can get too cold. So what’s a bird to do. Well, if you had been looking out my windows during the last storm (which would have been odd, since I don’t know you), you would have seen about 5 House Finches and a Northern Cardinal perched under the eaves of my neighbor’s house. I had a House Finch sitting on my drain pipe, right under one of the eaves, and a Carolina Wren perched on my front porch. Birds find places to shelter themselves from the heaviest rains to keep their feathers dry. Even leaf-less bushes and trees offer a lot of protection in a bad storm like that.
So next time it rains, check your drainpipes and eaves for birds. Or better yet, go set up a nice, big umbrella near your feeder and watch them kick back and wait for the storm to end.