Bird vocalisations are considered to be one of the most complex forms of communication within the animal kingdom, and have been studied for centuries, trying to get to the bottom of every whistle and chirrup. Being able to understand birdsong is the Holy Grail for many ornithologists, keen to elaborate on evolutionary theory as well as the simple desire to know what on earth they’re all going on about.

The tiny wren can trill out it’s 103-note song in 8 seconds, producing sometimes upwards of 110 decibels.

We tend to refer to any bird vocalisation that we consider as melodious as “song”, and any other sound as a “call”. In more technical terminology, the songs are the complex, lengthy multifunctional sounds, associated with courtship, mating, and territory, and calls tend to be typically monosyllabic, used for sounding an alarm such as when a predator is nearby, or contacting members of a flock, perhaps to enable a good grouping during flying.

How and why

The voice box of a bird is called a syrinx, which means panpipe in Greek. This double-barrelled structure is a remarkable organ, pun intended, as it sits around the junction of the trachea when it splits off into two as part of the magnificently efficient breathing system in birds. This design makes it capable of producing two different pitched sounds at once, or as with the wood thrush, a rising and falling note at the same time. Some birds such as the northern cardinal can produce a breath-taking repertoire of song by switching between the two sides, producing more notes than there are on a piano in a tenth of a second. The constant flow of air, combined with some incredibly powerful muscles, can also produce ear-splitting sounds as well as beautiful melodies. The level considered to be safe for the human ear is 85 decibels: the tiny wren can trill out it’s 103-note song in 8 seconds, producing sometimes upwards of 110 decibels, making it the loudest bird in relation to its size. The world’s loudest bird, the male bellbird, emits a brain-numbing 125.4 decibels during its two-note courtship song. That’s the equivalent of standing next to a jet fighter taking off, afterburners on full blast.

All of those sounds are performed for the same purpose – attracting attention.

Our scientific world classes true songbirds as being from the order Oscine, which makes up almost half of all bird species that exist, composed of thrushes, wrens, larks, warblers, and so on. We know that true songbirds learn their songs from the older generations, in a one-sings / one-repeats process, and fledglings can be heard practising them in the summer months.

Depending on who you talk to, the category can also include those birds who only ever sound the one note, like pigeons or sparrows, and even those other birds who don’t use a voice box but instead emit other sounds such as the clattering of stork bills, the drumming of the woodpecker bill on bark, and the ethereal “winnowing” of the snipe, a sound actually made by its tail feathers. All of those sounds are performed for the same purpose – attracting attention. But this takes a lot of energy and also announces the bird’s location to predators. Why do it?

For many years, birdsong was considered to only serve two functions: finding a mate and marking a territory. This is undeniably true, of course; in migratory birds for instance, males usually arrive at their destinations before females, and to establish a firm territory to win the affections of the incoming females, they will sing all day, every day. Birds like male golden orioles will start their territorial ululating from around 4 am onwards in the spring mornings, and usually keep that up well into late afternoon, telling other males this is my patch, go find your own. When the females do arrive a week or two later, if they’ve managed to hold on to a nesting site for that long, they must be worth it.

But the view that birds only sing to guard their love nest for future liaisons relied on the now debunked theory that males are the ones doing all the singing; misidentification of birds who have few physical differences between the sexes combined with a good deal of confirmation bias played a large part in reaching that conclusion, but recent work has discovered this is simply not the case. The females of some species either have their own set of notes entirely, implying another function, or take parts in duets long after mating has been established. It has also been observed that both male and female birds will change their songs over the seasons to more and more elaborate phrases, we think, to impress others. It has therefore been concluded that birds also must simply enjoy singing, and much like we do, like to show off if they’re good at it.

Music to our ears

Birdsong has of course moved us since time began, and influenced poets and musicians for centuries. So familiar was the sound of birds that it soon crept into the creation of our own music and song, forming the basis for many well-known works today. Two very popular birds during the height of classical music compositions were the cuckoo and the nightingale, both inspiring Handel, Beethoven, Vivaldi, and Mozart. The skylark can hold its tune for an unbroken 18 minutes, and was of course the inspiration for Vaughan Williams' The Lark Ascending.

‍Over thousands of years, we have conditioned ourselves to listen out for birdsong to reassure ourselves that all is well. The presence of birdsong has some kind of primal indicator to us – if you can hear it, things are considered fine, almost daydream-like. If you can’t, or if it suddenly stops, something feels very wrong.

Birdsong induces both physical relaxation but also, importantly, mental stimulation.

Birdsong is being put to remarkable use in our modern times. Because it is stochastic, that is, made up of lots of randomsounds, it has been shown to be very calming for humans, as there is no repeating rhythm or pattern to focus on. Unlike the distracting sounds like traffic, thumping music, children playing or loud conversations, sounds we strive to block out so we can concentrate, birdsong induces both physical relaxation but also, importantly, mental stimulation. It is now being used in situations that humans tend to find stressful but unavoidable, such as transporthubs. Amsterdam’s Schiphol airport, for instance, pipes recordings into a lounge where passengers can wait before their flights, and is played through speakers hidden in real trees. As well as schemes involving doctors “prescribing” nature and engaging in activities such as birdwatching for people suffering from various ills, people are now researching the possibility that birdsong can also be “administered”. There has been a wonderful study in a Liverpool, UK, school: after lunch, birdsong was gently played into classrooms. Instead of giving in to that productivity-denying postprandial somnolence, or as many of us who have tried to stay awake in offices know it as, the post-meal slump, the children were far more alert and able to concentrate after scoffing down their sandwiches.

A song for the dying

One incredibly touching way of harnessing birdsong was pioneered a couple of years ago in Wales, UK. A small hospice for children with life-limiting disorders hit upon the beautiful idea of commemorating the children who were cared for there by translating their names into birdsong. Using an old calendar that detailed which bird sang the loudest each month, sound artist Justin Wiggan would input the name of the child into a Morse code translator, and then use samples of the birdsong from the month that the child died, “creating” their name in birdsong. Over 300 names have been translated so far, and are now played outdoors in the memorial garden, where parents can visit and hear their children’s names in the air.

Based on what we know about birds learning songs and adding to their vast catalogue of sounds, it is Justin’s hope that in time, the birds that frequent the gardens will eventually learn the names, and each spring, will teach them to their children as well.