By Siddharth Unnithan Kumar and Kevin J. Gaston
The natural world (of which humans are a part) comes alive to us through our sensory systems. The soughing wind and pulsing ocean tides, leaves rustling and rain falling, the joy of the dawn chorus and tranquility of its dusk counterpart – these are some of the sounds which many people consider vital for their connection to, and experience of, nature.
Given the importance of sound and auditory perception to nature experience, we wanted to explore how hearing loss can change the way people interact with other species and experience biodiversity. In this paper, we focused on the possible effects of ageing on a person’s ability to hear birdsong. Ten species were chosen for our study (or, depending on how agency is considered, one might say that they chose us): the Robin, Goldcrest, Wren, Blue tit, Wood pigeon, Blackbird, Chaffinch, Nightingale, Cuckoo, and Sparrowhawk.
Our investigation began by using audio recordings of birdsong from the citizen science repository xeno-canto to derive a frequency-amplitude spectrum for each of the ten species (see Figure above). These are graphs which give a measure of how loud different components of a bird’s song are. Then, following a method employed by ornithologists Michael Emlen and Robert DeJong, we superposed public health data of age-related hearing loss onto these song spectra. From these overlayed images, we estimated how the perceived loudness of birdsong may change for people of different ages.
Our results highlight how the extinction of nature experience can disproportionately affect people with significant hearing loss. For example, birds such as the Goldcrest and Blue tit, who sing at higher frequencies, may become inaudible for older listeners even at distances of 5-10 metres. Moreover, because higher frequencies are generally lost with age to a greater degree than lower ones, birdsong can become not only quieter but also unrecognisable or undifferentiable from other sounds.
One notable implication of these results is that the description of bird calls provided in ecology textbooks, field guides, and signboards may be meaningful only to those people with good hearing. The key point here is that these descriptions provide information on a particular (not universal) perception of birdsong, which may include some people’s experiences and exclude others. In other words, such information in ecology textbooks and field guides is not of a bird as an entity separate from humans but rather is of a relationship between human listener and singing bird – the subject and object of perception cannot be separated.
We advocate for greater attention to: (i) the central role of sensory perception in human-nature interactions; (ii) how the extinction of nature experience can affect people disproportionately, solely as a result of sensory capabilities; and (iii) the potential for interventions – such as hearing aids, and better access to bird habitat – to restore people’s connection to, and sense of belonging within, the more-than-human world.
Relational Thinking 