About bird songs

About bird songs

This section is designed to answer the following questions :

  1. How do birds sing ?
  2. Why do birds sing ?
  3. Bird songs : instinct or learning ?
  4. Imitations and odd songs

 

1.How do birds sing?

Bird songs can appear astonishingly loud, fast and highly modulated (quick transitions from high pitched notes to low pitched notes). When trying to imitate them, we are immediately confronted to the limits of our own vocal organs. For example, unlike us, songbirds are able to produce two different pitches at once.

1.1. Difference between bird songs and human songs

Comparison between an opera singer (left) and a Booted warbler’s song (right).

Let’s look at this comparison between an opera singer (left) and a Booted warbler’s song (right).

On human voice, there’s a main signal around 1kHz, followed by higher attenuated harmonics with an identical shape. In a classical talk, only the lower harmonics are visible. On Cetti’s warbler, the range covered by the main signal is much wider (1-5kHz), and the transition between high-pitched notes and low-pitched notes more brutal. Several different sounds can overlap at the same time.

1.2. The specificity of a bird’s vocal organ : the syrinx

Such vocal performances are possible because birds do not have vocal chords, but an organ called syrinx. This is a two-sided vocal organ, located where the trachea splits into bronchial tubes.

Representation of a human larynx (on the right), compared to a bird’s syrinx (on the left)

 

The Cornell Lab of Ornithology has produced a remarkable interactive animation to explain how various songs can be produced into the syrinx :

See how a bird’s syrinx works 

 

2. Why do bird sing ?

Singing all day long is draining and increases the vulnerability to predators. Thus, to remain an evolutionary stable strategy, singing must be under a huge selective pressure.

There are indeed major benefits in singing : studies have also shown that songs play a crucial role in attracting potential mates. The quality of the sound may signal the overall health of the singer. Songs are also used to defend a territory.

Black-throated green warblers (Setophaga virens) in a dense forest. © Stanislas Wroza

Why songs are a good solution ? As birds tend to live in dense habitats, acoustic signals carry messages much further than visual signals. It’s also worth considering the fact that an acoustic battle costs less efforts that a real fight when it comes to competition for a partner.

 

3. Bird songs : instinct or learning ?

This question has been much discussed in scientific literature. While it is proven that some birds can learn and imitate almost any call, it is also established that birds bred in captivity do sing. Is the complex song of songbirds somehow written in their DNA ? To what extent can we talk about a learning process ?

Experiments have been carried out at Cambridge University.  Newly-laid Chaffinch (Fringilla coelebs) eggs were put in soundproof chambers. Even when nearly adults they sang very simple songs, representing as the experiment intended, the inborn component of the song. In the wild, Newly born birds listen and memorize songs from their neighborhood. It is only later, after they’ve fledged, that young birds start to practice. These first songs are messy and unstructured, a lot like the babbling of a young child. After many months of practice, songbirds settle on a repertoire, which then generally stays fixed for the rest of their lives. For these reasons, the vocalization produced by young birds in late summer can be a serious pitfall when identifying a bird.

Indian hill mynah (Gracula religiosa). ©Subramanya C.K.

 

There are also species whose song is inherited culturally, generation by generation. One such species is the Indian hill mynah (Gracula religiosa) commonly kept in captivity for its talking ability. It has been proven that the entire repertoire is learnt by ear from its elders by each season’s crop of youngsters. Yet, wild mynahs don’t copy other species. So how does the bird choose? The suggestion is that each learning species has an innate neural predisposition to attend only to the language of its own species

 

 

4. Imitations and Odd songs

Some adult birds still learn other songs and even add them to their own repertoire. This happens for some species like Marsh warbler (Accrocephalus palustris) that is famous for its ability to imitate over a dozen of birds in a single song. Parrots are well-known for their ability to imitate various sounds, including human voice.

Marsh warbler (Accrocephalus palustris). ©Stanislas Wroza


This Marsh warbler is imitating several birds including Woodpeckers, Great tit, Marsh tit, Greenfinch…

 

One other surprising encounter I had was this Great tit (Parus major) producing an almost perfect imitation of Common chiffchaff (Phylloscopus collybita) in winter, showing that almost anything can be expected.

But the award of the craziest examples of bird “artistic composition” goes to a  Crested lark (Galerida cristata) in Bavaria according to Erwin Tretzel’s paper “Bird Banding”. The bird imitated and combined the four whistled commands a shepherd used to work his dog. Not only did it imitate the whistles, but he also combined them to create a genuine melody. It “employed fairly accurately the intervals of the scale of C Major” and “presented its shepherd imitations mostly in a pleasing arrangement with definite metrical construction that revealed an astonishing sense of feel of the singer for musical form and proportion” !!!

Crested lark (Galerida cristata).©Stanislas Wroza

 

Finally, It also happens that some birds repeatedly produce odd sounds and do not sing “normally” at any time of their life. A frequently raised hypothesis is that some of those odd-singing birds are actually deaf, so they cannot adjust their song. Check this odd Common whitethroat (Sylvia communis) :

 

So now that you know everything about bird songs, always be wary  !

 

Read the next page of “The quick guide to soundbirding” : Sound and spectrograms

 

 

 

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