With the development of massive transportation infrastructures, most countries have become overrun with industrial sounds. Planes fly overhead, cars rush along the ground, trains and trucks and industrial sounds bleed everywhere. People are able to easily tune it out or work around it. We're able to phone, email, and text if things get too loud. If we had to walk through the heart of cities calling out for people we know, we might feel a little differently about it.
Birds have to do exactly this. Find out how driving around in your car indirectly effects the reproductive selection habits of birds, taking the sexiest birds out of the running.
In order to find each other, especially for first dates, birds have to call, and the technology we made is drowning out the physics they rely on. Low frequency sound waves have long wavelengths. These waves bend around barriers and are not easily absorbed by air molecules, and so they travel long distances. This is why people can hear the rhythm of a song in a passing car, but not any of the lyrics. Birds sing in, what is for them, low frequencies. These calls reach far, and are traditionally the sexiest calls for female birds. They're also utterly drowned out by the louder, lower frequencies of today's technology.
High frequency sound waves have short wavelengths that don't carry as far. They are more noticeable at short distances, and against a backdrop of low frequency sound. This is why the mocking laughter of children will cut through the background sounds of a crowded room, bringing everyone to attention and haunting your dreams forever. Although it's not preferred by female birds, it may be the only possible sound that they can hear in certain situations. Instead of their traditional low-voiced mates, birds are switching to partners with high-frequency calls. Even male birds are pitching their calls higher.
The technology of today may be giving rise to new, sexually-selected species of birds in the future. There's no way to be sure what they'll look like, but they're sure to have an ear-splitting shriek. So enjoy that, future generations. Do enjoy that.
Image: Patti McNeal