A Bird's Song

We hear them everyday, we hear them in our backyards and we hear them in the forests. Bird songs can be heard everywhere. Birds songs are nature's best sounds made by birds which are melodious to the human ears.

Ornithologists classify birds vocalisation into two types, which are :
(1) Bird Songs

(2) Bird Calls

Bird Songs are the longer and more complex bird vocals and are usually produced by birds in matters related to courtship, mating and territory. Many birds exhibit temporal and contextual variation in their delivery of songs, and in their responsiveness to the songs of members of their species. These variations

include short-term changes, such as locations in their territory, proximity to conspecifics,
and longer-term variations, such as with phase of the nesting cycle, time of day or season,
and even in relation to weather conditions such as temperature.

Bird Calls are comparatively simple, shorter and less rhythmic vocalisations which serve the function of alarms and to call for a partner or flock of that particular species.

The birds which are broadly classified as songbirds are Warblers, Thrushes and Sparrows. Songbirds learn their songs and perform them using a specialized voice box called a syrinx.The vast majority of non-songbird species make simpler sounds that are instinctual rather than learned. While some birds hatch knowing the songs they will sing as adults, the true songbirds have to learn how to communicate effectively. Songbirds begin learning their songs while still in the nest, a phase known as the critical period, when nestlings listen to the adults singing around them. Following fledging, young birds attempt to replicate these songs, practicing until they have matched their tutor's song. Some songbirds, such as the catbirds, thrashers, and mockingbirds, learn to mimic other species—frogs, cats, and even car alarms.

Unless and until we make an effort to hear a bird call it goes right through our heads. Each and every bird has a distinct sound, even the slightest of vocal differences can can help us differentiate between two species of birds, yet we can't recognise or remember the unique voices of all the birds. Thankfully, we have tools to represent bird calls visually through graphs which shows us the difference between vocal fibrillation of bird sounds. 

Grey Breasted Prinia

In the this graph we see that the frequency of the Grey Breasted Prinia is extremely low and can be heard loud and clear. The red area shows us the frequency until 44 Hertz and the purple shows 20500 Hertz. Humans can hear sounds  from 20 Hz to 20000 Hz .

Grey Breasted Prinia sound frequency graph

Plain Prinia

This graph shows the calls of the Plain Prinia and as we can see it has a higher pitched voice in between 1440-1830 Hz.

Plain Prinia sound frequency graph

If you hear a bird call or song the chances of that bird being male is greater. Male birds are the ones who produce most of the songs and calls in order to attract partners and assert their territory. Many birds sing at dawn. I believe that these calls are used by male birds in defence of their nests and mates. Particular birds such as the Pitta family burst out in a pompous and loud display of their calls at dawn and dusk. Birds are excellent vocalists. The "Thrasher" family of birds can produce two different notes at once. Canary's can alter between high and low notes by switching sided of the syrinx.

Indian Pitta 

Indian Pitta sound frequency graph.

Owls are also an interesting species when it comes to vocalisation. Many owls vocalize at a distinctively low frequency, which allows their songs to travel long distances without being absorbed by vegetation. Becoming familiar with these songs and other vocalizations will help you find and identify owls. Their calls are usually hoots, screeches, barks and shrieks.

Indian Eagle Owl

Indian Eagle Owl sound frequency graph.

Waveforms show changes in loudness over time. Distances between peaks are used to calculate pitch.

In todays world bird songs are being heard less and less everyday. The harsh and loud sounds created by vehicles, factories, and human tools cover up these beautiful and complex vocalisations made by birds. People use recorded audio calls from the internet or call playback to attract birds for the purpose of hunting them or for bird watching. This has increasingly become a problem in India.  The overuse of such artificial methods can affect breeding habits and social behaviours of birds.

The growth of bird song research over the past half century has been catalysed by both technical and theoretical advances. The study of mechanisms has largely moved to the neurobiological level, where work on bird song has blossomed. The vast topic of  bird vocalisation cannot be covered by one single article and one can even go very deep into the details of bird calls of a single bird species. I hope everyone observes more bird sounds from now on.