I was wandering through the forest in western Washington when I heard a series of high-pitched, whistling bird calls. As I peered into the foliage, I finally made out the Cedar Waxwings that were making the sound. Another time, I was in southern Texas, along the Rio Grande border. Again, I heard birds singling some very high notes. In this case, they were followed by a series of lower notes and a distinctive two-tone call. I realized that I was surrounded by a number of Ruby-crowned Kinglets.
Can plants hear? At first glance, this seems like a silly question. Plants don’t have ears, so of course they can’t hear. But wait—do organisms need ears to hear? What is hearing, anyway?
Given that sound consists of a series of vibrations that are propagated through air, water, or another substance, then hearing must be the ability to sense those vibrations. And while our ears are very good at sensing vibrations, there are other options.