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24 September 2014

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You are in: Devon > Nature > Nature Features > Why do birds sing?

A robin (RSPB)

Robins say 'tick tick' when worried

Why do birds sing?

Tony Whitehead, education officer for the RSPB in the South West, ponders an apparently simple question.

Birds use their voices to communicate with other birds. Using voice is a particularly efficient way to communicate over distance, especially when you are small and live in dense habitats such as woodlands.

A bird call says something clear and unambiguous about the caller (I'm a robin and I'm worried about that cat down there is 'tick, tick tick').

And, as communication is a two way thing, these calls have to influence the behaviour of the birds listening (that robin 'tick, ticking' over there is worried about something, I'd better be on my guard too).

Bird song is a very specialised form of bird call that, unlike all the quacks, honks and tweets we hear throughout the year, serves one function only – to ensure the breeding success of the singer, to indicate clearly that the singer is healthy and fit and ready to breed.

A song thrush

Songthrushes have a highly developed bird song

It's largely a boy thing, designed so that other females of the same species are attracted and males of the same species are repelled.

Bird song is most highly developed in a group of birds called passeriformes. Don't worry, we are surrounded by them, wrens, robins, blackbirds, song thrushes are all passeriformes.

Basically it means 'perching bird' and it's an enormous group – around 5,400 of the world's 8,000 to 9,000 species are 'perching birds' and all of them sing. Differently.

Theme tunes

Each species has its own signature song, its own theme tune. Some are pretty basic, chiff-chaffs just go 'chiff chaff', but many are rich and complex and never fail to lift the spirit – blackbird immediately springs to mind.

Each song is different, because, first of all it has to identify the singer's species.

Females need to know this if they are to choose the right partner! Then, the song has to say something about the health of the singer. A long, loud song for instance indicates a certain amount of stamina, a bird in good condition.

Similarly with repertoire. It appears that in some species, a wide variety of sounds in a song is especially attractive to the ladies. Many species even mimic other birds' songs just to increase their repertoire, and it's not unknown for other sounds, such as cats' calls, to be included as well. 

A blackbird (PIC: RSPB)

Blackbirds always sing a lovely song

All this, just so that the female can judge the quality of a potential father.

For other males too, simply listening to a song delivered with bravado will often be enough to cause them to seek space and females elsewhere.

And this, most importantly, saves them having to come to blows to see who's the best, which long ago, bird evolution determined was a massive waste of time and effort and very much a last resort. 

As bird song is part of the breeding cycle, most birds sing in the breeding season. This means that birds will start singing in late January and stop singing in July.

They are prompted to start singing, it appears, by increasing daylight (more light sets their little hormones racing and in response, they sing).

They stop singing when they start moulting, usually July time, as the last thing you want to do when your feathers start falling out and you are not quite as quick off your perch is to advertise your presence to predators.

Some birds, of course, sing in winter, robin being the best known, but this is linked to defending feeding territories rather than breeding. Interestingly, in winter, female robins sing as well as males.

Just as there is a seasonal cycle to bird song there is also a daily cycle, with the most intense period being at first light, the so called 'dawn chorus'. Why sing so intensely at dawn though?

Starling: Devon's number six

A starling (RSPB)

First of all, male birds may die overnight if they have not been able to feed well during the previous day. 

So, first light is a time when when birds can announce their survival, and this advertises something of their feeding abilities to potential mates - and of course, it's important that females know if males can find food or not, especially when they will be relying on this after their chicks have hatched.

Also, a side product is that birds looking for territories can hear where the spaces are and move in.

Secondly, many females lay eggs at first light and immediately after this are at their most fertile. This is a time when males need to fend off other potential suitors, and as we now know, song is a key way they do this.

Hence the dawn chorus. 

Well, this is what is suggested and there are a few other suggestions as well, such as dawn being a still, quiet time and thus sound carries better. Another theory is that because birds can't feed in early light, they sing to occupy the time.

What this indicates is that the study of bird song is still, in the history of zoology, quite a new science.

Gilbert White back in the late 18th Century made some early observations, but it wasn't really until the advent of the sound recorder that zoologists could 'capture' and analyse the sounds thoroughly.

So, while much is known, there's a lot still to learn. Even the ubiquitous song of a starling might contain complexities on the edge of human understanding.

last updated: 15/04/2008 at 16:49
created: 03/04/2008

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