A long time ago, a philosopher walked into the forest, unanchored in his inner sea of wonderings. He was an unusually quiet fellow, according to his peers, but this was only his outward-facing self. Inside, he was like a boiling tea kettle, questions and observations constantly ready to be poured into his notebooks. Occasionally, the words would slip out like steam when he was alone.
On this particular day, the philosopher wandered the woods after a refreshing summer morning rain. He noticed the mosses and lichens were reinvigorated, especially verdant after the fresh watering. Look, how they seem to coat the living trees and the logs– thought he, gently brushing his fingertips over a delicate fern-like moss growing over a particularly large log. He turned his gaze skyward, the hole in the canopy left behind by this great behemoth of a tree absent, overtaken by the trees which had grown in around it.
“If a tree falls in the forest, with no person around to hear it, will it make a sound?” the philosopher asked the moss.
“Yes,” sang the sparrow, whose nest was tucked into a thicket of spicebush nearby. “For there are more than human ears!”
But the philosopher did not perceive the reply, and so he believed he posed a great philosophical mystery– in the minds of men, perhaps he did. But the sparrow was learnéd, too.
As time persisted, the sparrow raised many fledgling sparrows, singing while they grew so they might too know how to sing out across the trees and lakes. Soon, the trees and lakes changed by the hands of man, and instead of wide expanses of forest, there were great clearings, where they constructed nests taller than the trees. The sparrow passed before he saw these things, survived by his fledglings who now built their own nests amongst the grand human structures.
They remembered him through their songs, each spring singing to declare which land was theirs, and to entice a mate.
But as the trees dwindled, the shrubs removed, and the human nests built in their place, the sparrows who lingered in their lands struggled to find each other. In the high spring mornings, their songs were accompanied by the thundering cars bustling between structures, and the low notes could not carry above the city peal. Even the wind thought some notes were too heavy.
In time, the habitat was planted with green again, inviting the sparrows to nest among people. The sparrows still sang, but pieces of their language were lost, buried under the city music of engines and innovation. The nestlings became fledglings, their father’s songs becoming their own, modified to the crescendos around them.
***
Some birds have adapted to the human landscape and are able to live in cities because of their physiology: the study of how the body functions. Many species inhabiting urban areas are able to do so because they have physiological adaptations and behavioral adaptations. This means their body experiences changes, usually through the production of various stress hormones, that help them survive. For example, some birds, such as Song Sparrows, can be found living closer to cities because they have physiological adaptations that help them manage the stress of cities.
Songbirds such as sparrows usually sing during the breeding season as a means of declaring territory boundaries, and attracting mates. Different species will vary drastically in the types of song, and the way song is acquired. Some will sing the same song year after year, while others demonstrate greater variation. Song Sparrows, for example, have been observed with up to 15 variations of a song.
Song Sparrow (Melospiza melodia) photo by author
So, why then did the sparrows in the fable lose pieces of their ‘language’? Well, anthropogenic (human-caused) noise has always been part of the landscape. However, with industrialization, the soundscape has drastically changed in the type and volume of sounds we make, and the way in which sound waves travel around us has changed. For Song Sparrows, this has led to a decrease in lower frequency portions of their song, because anthropogenic noise such as cars tends to mask these lower frequencies. Birdsong is important because of its relationship to other behaviors, such as nest-guarding and finding a mate. Both are vulnerable times in an adult bird’s life, because singing means they are more visible to predators. When a song has to change, either in the amount of time spent singing or the type of sound produced, it can have an impact on whether the bird survives to the next season.
However, noise affects birds near urban environments differently. In species which have demonstrated urban adaptability, there seems to be decreased levels of chronic stress on adults and nestlings. However, in species less adapted to urban areas, such as Tree Swallows, proximity to elevated traffic noise has been proven to negatively impact nestlings and adults due to the extended release of corticosterone, which is the stress hormone in birds. Birds experiencing this for a long period of time can experience challenges in having enough food and energy, because the chronic stress can decrease their overall body condition, just like in humans. This means they have a harder time recovering from stressful events, such as storms.
References:
Allison S. Injaian, Conor C. Taff, Kira L. Pearson, Michelle M.Y. Gin, Gail L. Patricelli, Maren N. Vitousek, Effects of experimental chronic traffic noise exposure on adult and nestling corticosterone levels, and nestling body condition in a free-living bird, Hormones and Behavior, Volume 106, 2018, Pages 19-27, https://doi.org/10.1016/j.yhbeh.2018.07.012.
Meelyn Mayank Pandit, James Eapen, Gabriela Pineda-Sabillon, Margaret E Caulfield, Alexander Moreno, Jay Wilhelm, Jessica E Ruyle, Eli S Bridge, Darren S Proppe, Anthropogenic noise alters parental behavior and nestling developmental patterns, but not fledging condition, Behavioral Ecology, Volume 32, Issue 4, July/August 2021, Pages 747–755, https://doi.org/10.1093/beheco/arab015
William E. Wood, Stephen M. Yezerinac, Song Sparrow (Melospiza Melodia) Song Varies with Urban Noise, The Auk, Volume 123, Issue 3, 1 July 2006, Pages 650–659, https://doi.org/10.1093/auk/123.3.650