Researchers of a new study reconstruct 200,000 soundscapes that reveal a patterned phenomena: the birds are disappearing.
Birdsong lures the poet like a siren’s call and lulls her to write. The avian’s cry has infatuated lyricsts since the dawn of time. Sappho, a poet of Greek antiquity referred to the “sweet-voiced nightingale” as the “spring messenger” in the late seventh century BCE. To 19th century poet, Percy Bysshe Shelly, “A poet is a nightingale, who sits in darkness and sings to cheer its own solitude with sweet sounds; his auditors are as men entranced by the melody of an unseen musician, who feel that they are moved and softened, yet know not whence or why.” The nightingale flies across time and through the pages of Ovid’s Metamorphosis and Shakespeare’s Titus Andronicus. It is amongst a vast flock of literary birds, from the caged singer of Maya Angelou to the Long Island sparrows of Anthody Hecht to the midnight raven of Edgar Allan Poe. What is classic poetry without such chirrs? What is the spring morning without the birds?
It’s quiet. And the only audible sound may be the wind.
Birdsong is one of the strongest natural sounds that constructs and maintains the human connection to nature. It conveys a sense of place and groundedness. A new study published this month in Nature finds that these sounds are changing, and a much quieter dawn of choruses awaits us. In fact, it has already begun.
As bird populations decline, acoustic properties of natural soundscapes diminuendo. Not only have these environments across North America quietened, but they have become less varied. An international team of researchers led by the University of East Anglia (UEA) developed a novel procedure in analyzing these trends: reconstructing the sounds of the past. To do so, they combined annual systematic bird count data from North American Breeding Bird Survey (NA-BBS) and Pan-European Common Bird Monitoring Scheme (PECBMS) sites with recordings of individual bird species from an online database. The result was a remake of 200,000 locational soundscapes expanding across two continents over the past 25 years. They did this by selecting the site-year count data files one by one and inserting the tweeting creature into a 25 second slot randomly, repeating down their lists until five minute clips were filled to the brim with melodic warbles and caws. Each species underwent soundscape protocol to monitor vocalization frequency. Furthermore, the researchers measured the characteristics of their soundscapes against acoustic indexes intended to reflect the richness, evenness, amplitude, and heterogeneity of the scapes. To quote the paper, “These acoustic indices are broadly correlated with avian species richness and abundance but are fundamentally driven by song complexity and diversity across contributing species.” Thus, these indices are crucial in describing key factors predicted to underpin public perception of nature experiences.
These reconstructions reveal previously undocumented changes in acoustic properties of soundscapes across North America and Europe over the past several decades. While the researcher’s results showed variation depending on region, decreases in frequency and diversity were observed. Why? Global biodiversity loss naturally breeds a chronic deterioration in soundscape quality. And while the focus here is on birds, the researchers hypothesize that the trends observed are likely parallel with other taxonomic groups who contribute to soundscapes. What are the tropical rainforests without the tymbal hums of Empress cicadas or calls of Golden-whiskered barbets? Or the riverside without the conversational croak of the bullfrog?
A vast array of biodiversity can be observed when listening to Thailand's temperate forest. Close your eyes and hear: the Asiatic Jackal’s howl, the Green Peafowl “ki-wao” song, the sharp nasal call of the Black-hooded Oriole, and the deep hoot of the horned owl. Would the forest be the same without these sounds?
The short and obvious answer is no. For without the sounds, the creatures do not exist.
Yet, sound is the first thing the public notices when it comes to biodiversity loss. The results of the study suggest that the fundamental pathways through which humans engage with nature is on the decline, a parallel negative slope with the sounds of the birds. This suggestion, the researchers say, has potentially widespread implications for both human health and wellbeing, as well as general care for our communal, global habitat.
As said by Dr. Catriona Morrison, a post-doctoral researcher in UEA's School of Biological Sciences, who conducted the analyses, "As we collectively become less aware of our natural surroundings, we also start to notice or care less about their deterioration. Studies like ours aim to heighten awareness of these losses in a tangible, relatable way and demonstrate their potential impact on human well-being."
This heightened awareness is needed because, as the researcher’s theorize, reduced nature connectedness may also be contributing to the global environmental crisis, as there is evidence it can lead to reductions in pro-environmental behavior. It is more than solely the loss of the chirping bird in the morning. It is a loss that is a tick in a negative feedback loop, whereby a decline in the quality of nature contact experiences leads to a domino effect of reduced advocacy, financial support for conservation actions, and thus further environmental degradation.
Without conservation policy or action, the sounds of our environments render into silence. In the absence of much notice to the quiet, one day it is wondered where all the birds drifted off too, until we wonder if we ever heard them chirp at all. What did they even sound like?
“Chew-chew chew-chew” and higher still,
“Cheer-cheer cheer-cheer” more loud and shrill,
“Cheer-up cheer-up cheer-up” — and dropped
Low — “Tweet tweet jug jug jug” — and stopped
One moment just to drink the sound
Her music made, and then a round
Of stranger witching notes was heard
As if it was a stranger bird:
“Wew-wew wew-wew chur-chur chur-chur
“Woo-it woo-it” — and could this be her?
“Tee-rew tee-rew tee-rew tee-rew
Chew-rit chew-rit” — and ever new —
“Will-will will-will grig-grig grig-grig.”
-“The Progress of Rhyme” (1835) by John Clare on the sounds of the nightingale.