The physiology of the avian vocal apparatus is a lot more complex than the human’s. Birds have an organ called a syrinx (named for the Greek nymph – this is a human name, not a bird one – ed.) that sits at the bottom of the trachea. The human larynx, by contrast, is at the top.
The membranes of the syrinx are controlled by muscles with a degree of nuance that humans cannot match. Furthermore, the lower anatomical position of the vocal organ – at the base of the bronchi – allows all kinds of neat tricks, including the ability to make two totally different sounds at once. This is employed in birdsong to neat effect.
Thus, whereas humans mimic environmental sounds with relatively low fidelity (a few outstanding exceptions aside), certain birds (passerines, or songbirds, in particular) can instantly produce dead-on impressions of anything they hear, from the calls of their relatives to the voices of other species to man-made machines in operation. Evolutionarily, this seems to be a means of demonstrating physical health for mating and combat, as well as communications. The birds with the loudest and most complex voices are obviously the fittest.
This is a famous video from David Attenborough’s BBC Wildlife series showing the superb lyrebird in action. It starts cool and then gets unbelievable, but you can believe it now because you understand a little about how it works:
Many questions open up after watching this bird imitate cameras, chainsaws, and car alarms. One of these is cognitive – how do birds process and store environmental information in order to reproduce it themselves? Another is philosophical – if humans, like birds, are material beings that respond throughout their lives to external stimuli, then where can we locate such precious concepts as agency, creativity, and inspiration? Are these really only human things, or do birds have them, too? Or are they suspect?
A third question, perhaps most germane to sound studies, is about the role of vocal mimicry in environments and ecosystems. The superb lyrebird’s speech not only suggests certain behaviors that evolution made inherent, but also makes clear just how closely the nonhuman world listens to our every action. The environmental movement has gotten us used to thinking about the consequences of our garbage, but we have only just begun to investigate how less tangible phenomena like sound can also affect living things. There is a small but growing body of work about how human and mechanical sound affect migratory patterns and stress levels in birds, particularly in urban areas.
Birds not only have more flexible vocal apparatuses than humans, but they also hear both above and below our range. As a result, much of what affects them will not be immediately obvious to us – we simply lack the anatomical means to be sensually sympathetic without further intellectual effort. The fact is that other beings, with different sensory equipment, inhabit sensory worlds that we do not. These sensory overlays, however inaccessible they may be to us, are nevertheless a critical part of ecosystems. In issuing sounds that we perceive as irrelevant, minimally intrusive, or simply necessary to development, we may well be wielding little bird LRADs, intruding on sensual territory in ways that can induce significant behavioral and environmental change. This is a process that we’ve only begun to study with any specificity, but the lyrebird’s imitations should alert us to its depth.