Na­ture’s finest song

The dawn cho­rus is a won­der of na­ture that is truly ap­pre­ci­ated by the early ris­ers among you – but how do birds sing and why do they do it?

Bird Watching (UK) - - Contents - WORDS: MATT MER­RITT

The dawn cho­rus is one of na­ture’s great­est glo­ries at this time of the year and we re­veal how birds sing and why do they do it

BY THE TIME you’re read­ing this, the chances are you’re wak­ing ev­ery morn­ing to one of the great glo­ries of the nat­u­ral world in Bri­tain – the dawn cho­rus. Seem­ingly ev­ery bird in the neigh­bour­hood lifts its voice to her­ald the com­ing of day­light, build­ing from a few hes­i­tant notes from early ris­ers like the Black­bird to a won­der­ful crescendo once ev­ery­one else joins in. This is na­ture’s alarm clock at its finest.

Now you don’t need to do any­thing other than ap­pre­ci­ate its own beauty, but if you can start to un­ravel some of this glo­ri­ous ta­pes­try of song, and start to iden­tify the in­di­vid­ual strands, you’ll find your over­all bird ID skills im­prov­ing, too. Species that you hadn’t thought were present in your area will re­veal their pres­ence. Now is the time your #My200birdyear list will start to grow and grow. But why do birds sing, and how? The an­swers, as you might ex­pect, are com­pli­cated…

Songs vs calls

Birds use their voices to com­mu­ni­cate be­cause it’s an ef­fi­cient way of do­ing so, es­pe­cially for smaller birds that live in habi­tat such as wood­land (and re­mem­ber that most of our gar­den birds are wood­land or wood­land edge spe­cial­ists). In­deed, some of the small­est birds, such as the Wren, have the big­gest voices, for just that rea­son. But not ev­ery sound that a bird makes from its beak is a song. There are calls, too – these are usu­ally short, clear, loud and un­am­bigu­ous, and each sig­nals some­thing dif­fer­ent. It might be to main­tain con­tact with other birds – lis­ten to a skein of geese call­ing to each other as they fly – or it might be to alert oth­ers to dan­ger, such as the un­mis­tak­able alarm call of the Black­bird. Song, though, is far more spe­cialised, to pro­claim a ter­ri­tory and to in­di­cate to oth­ers that the singer is healthy and ready to breed. For that rea­son, of course, birdsong peaks dur­ing spring, when there’s lit­tle else on a bird’s mind.

Who sings?

It’s a strat­egy that’s most fully ex­ploited by a group of birds called Passer­i­formes, lit­er­ally, ‘perch­ing birds’, which make up around 60%

of the world’s 10,000 or so species. And it’s usu­ally the males that sing, although there are ex­cep­tions, such as Robins, where both sexes do so.

What does the song mean?

Firstly, it iden­ti­fies the bird to oth­ers of its kind (and, of course, to you!). Se­condly, it says some­thing about the phys­i­cal con­di­tion of the singer, so that any lis­ten­ing fe­males can choose a mate in good con­di­tion, with the stamina to breed and then (in many cases) feed a fam­ily. To some ex­tent, the male bird is say­ing ‘look at me! I’m so suc­cess­ful, I can af­ford to spend time and en­ergy on singing this song, rather than for­ag­ing for more food’. Thirdly, it warns off other males who might be think­ing of muscling in on our singer’s ter­ri­tory and/or mate, with­out them hav­ing to come to blows. Again, evo­lu­tion has fas­tened on the most ef­fi­cient way of per­pet­u­at­ing the species – ac­tual phys­i­cal bat­tles could be dis­as­trous for both of the birds in­volved.

When do birds sing?

For the most part, in the breed­ing sea­son, roughly from the start of Fe­bru­ary to July, when they start moulting and have to think about stay­ing hid­den from preda­tors. Again, there are ex­cep­tions – Robins sing through­out the win­ter, although that’s to de­fend feed­ing ter­ri­to­ries (hence why fe­males sing, too), and Mis­tle Thrushes, too, are known for singing in mid­win­ter (hence their old name of Storm­cock). For most birds, though, the in­stinct to sing is trig­gered by an in­creased amount of day­light as win­ter starts to move into spring.

Robins sing through­out the win­ter, although that’s to de­fend feed­ing ter­ri­to­ries (hence why fe­males sing, too), and Mis­tle Thrushes, too, are known for singing in mid­win­ter

What is so spe­cial about dawn?

There are sev­eral rea­sons why so many birds sing at dawn. For a start, the male birds are an­nounc­ing their sur­vival of the night, no small feat when preda­tors, weather, and the con­stant need to find enough food is con­sid­ered. A male that has sur­vived is not just avail­able for breed­ing – he is telling any fe­males lis­ten­ing that he’s eas­ily able to sup­ply him­self (and po­ten­tial mates and chicks) with enough food. Se­condly, there’s a ter­ri­to­rial func­tion. Males are ward­ing off other males, so that vi­tal food sup­ply is not overused. For other males, song helps de­lin­eate ter­ri­to­ries, and re­veal any gaps where they could set up on their own. Thirdly, many fe­male birds lay eggs at first light, and are at their most fer­tile im­me­di­ately af­ter­wards, so singing serves to ward off other males who might be think­ing of at­tempt­ing to mate with them. There could be other ben­e­fits, too. Dawn is gen­er­ally quiet and still, so sound car­ries fur­ther (this is also the rea­son sug­gested for ur­ban Robins singing at night), while some species are un­able to feed at dawn and so might as well spend the time do­ing some­thing else. Tak­ing this last point, there’s cer­tainly a log­i­cal pro­gres­sion in the way the dawn cho­rus de­vel­ops – birds that feed on fly­ing in­sects, for ex­am­ple, have to wait un­til the day has warmed up a lit­tle and their prey has be­come ac­tive, while those that eat worms can start ear­lier. So, Robins and Black­birds sing early, and get the worm, as the old proverb sug­gests, while war­blers gen­er­ally join the cho­rus later. Fi­nally, there’s also a dusk cho­rus. It’s not quite as all-in­clu­sive or as loud as at dawn, but many species do join in, and for many of the same rea­sons as at the start of the day.

How do birds sing?

OK, here’s the sci­ence bit. Ba­si­cally, a bird takes in air through its bill, on into its wind­pipe (or tra­chea). This then forks off to each lung, and after the air is pro­cessed there, it is ex­haled by the same pas­sage. This sys­tem has the sec­ondary pur­pose of pro­duc­ing sounds. The bird has a ‘voice box’, called the sy­rinx, at the point where the wind­pipe di­vides. This is ef­fec­tively dou­ble-bar­relled, and al­lows birds to pro­duce two dif­fer­ent sounds si­mul­ta­ne­ously, ob­vi­ously of great ad­van­tage in build­ing a com­plex song. Each half of the sy­rinx con­sists of a pair of or­gans op­po­site each other on the wall of its bronchus – a lit­tle tym­pa­num, or elas­tic mem­brane, which is ef­fec­tively a vo­cal chord, and a small lump of tis­sue. The bird forces air past these two or­gans. The di­am­e­ter of the tym­pa­num can be var­ied, and the de­gree to which it pro­trudes into the bronchial tube, and sound is cre­ated by the pass­ing air vi­brat­ing the tym­pa­num. Its pitch and loud­ness can be var­ied by the size and po­si­tion of the tym­pa­num, and the lump of tis­sue (which is ex­tend­able) is thought to help change loud­ness with­out chang­ing pitch. Given that each half of the sy­rinx can work in­de­pen­dently of the other, you can imag­ine how some song­birds can pro­duce mu­sic of ex­tra­or­di­nary com­plex­ity. For those birds which sing par­tic­u­larly long songs, too, the abil­ity to sing while in­hal­ing is ob­vi­ously a ne­ces­sity. The end re­sult is an ar­ray of sounds more com­plex than any oth­ers in the nat­u­ral world. Func­tional, prac­ti­cal, vi­tal for life, yet beau­ti­ful, too – no won­der birdsong has al­ways in­spired hu­man mu­si­cians, po­ets and other writ­ers. Just as when you’re learn­ing a for­eign lan­guage, for hu­mans, learn­ing birdsong is best done stage by stage, start­ing with the sim­plest and/or most com­monly heard songs. Tak­ing your time and hear­ing the same song over and over again is the key – you’ll be sur­prised how eas­ily you ‘get your ear in’. Once you’ve mas­tered some of the ba­sics, you’ll find that un­usual songs stand out, even in a dawn cho­rus or a noisy spring wood­land. Here’s our quick guide to learn­ing 10 bird songs. Re­mem­ber that sim­i­lar songs don’t al­ways come from sim­i­lar species, so be pre­pared to think lat­er­ally. Get to grips with these, and you should soon be able to iden­tify 20 more…

LIQ­UID SIL­VER The Robin’s song is fa­mil­iar, beau­ti­ful and ex­quis­ite

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