By Richard Collins
THE ROBINS have been singing all winter but most of our feathered friends remained silent during the dark months.
Now, in my neck of the woods, wrens, blackbirds and thrushes are practising their scales and arpeggios. Spring is coming but it’s still a long way off, so why are birds singing so soon? Putting on a concert would seem to be a pointless exercise and a dangerous one as well. There are no leaves on the trees and shouting your head off from a bare branch attracts unwelcome attention. The local sparrowhawks and cats will enjoy your recital.
According to science, birdsong has two functions. It enables the singer to stake out the boundaries of his territory and it informs prospective females of his availability as a mate. According to poets and mystics, however, birds sing for the sheer joy of it. In the poetic imagination, birds exult in the beauty of morning sunshine and celebrate the gift of life, just as we humans do. Such ideas, however, have no place in the scientist’s arid scheme of things.
In his recent book, Why Birds Sing, David Rothenberg expresses his dissatisfaction with the scientific account of birdsong.
Coming from a musical, rather than a scientific perspective, he points out that birds do far more singing and indulge in much more elaborate songs than could ever be necessary if they were simply proclaiming territories and securing mates. Nightingales hold forth for hours on end, even when there is no rival in the vicinity nor any prospective female to seduce. There must be more going on in birdsong than we think. The standard scientific model, Rothenberg believes, is just not adequate. However, his book is not particularly illuminating when it comes to offering an alternative explanation.
He evades the hard questions and instead draws out parallels between human and bird music. He celebrates the extraordinary beauty of birdsong but ultimately, he is at a loss for a theory.
But Rothenberg has a point and it has not gone unnoticed by science. It is known as the problem of "redundancy". The term comes from telecommunications engineering and describes the unnecessary and useless bits of information which always accompany the transmission of signals.
The modern craze for text messaging illustrates the point. In the hands of a competent text message sender, a peeled-down text carries the required information and nothing else. Spelling conventions are abandoned and punctuation marks are excluded. Ordinary mail is far more longwinded and labour-intensive. Compared to a text message, does a written letter convey additional information of any value? In engineering parlance, the letter contains ‘redundancy’.
The avian equivalents of the text messengers are species such as the great tit and the chiffchaff, which have minimalist songs. Their repertoires are built up from only two notes. In the case of the great tit, the notes are blasted out in quick succession. An individual will vary the rhythm and the tempo occasionally. A great tit can have up to seven versions of his simple two-note burst.
The chiffchaff’s offering is a little more complicated; he doesn’t change the tempo but, instead, varies the order in which the two notes are sent. We humans don’t speak the chiff-chaff’s language but it is tempting to think of his song as a digital transmission of ‘ones and zeros’. Whether it is digital or not, it is a very simple song with little redundancy.
Some of the chiffchaff’s cousins, on the other hand, have most elaborate songs. Rothenberg cites the marsh warbler, a bird whose song consists of phrases borrowed from other birds. Marsh warblers breed in Europe but spend the winter in Africa. Their plagiarised recitals include phrases lifted from birds all along its migration route.
Marsh warblers don’t breed in Ireland but one of our own warblers has a repertoire that is equally elaborate.
The sedge warbler is a familiar bird of Irish marshland. Its song is unbelievably complex, consisting of thousands of notes, a sort of vocal equivalent of the peacock’s tail. That it should be so elaborate is all the more remarkable because sedge warblers don’t sing to defend their territories but only to attract a mate. Once he secures a partner and ties the knot, a sedge warbler does not sing again.
His recital consists of an elaborate series of individual phrases, each with its own distinct rhythm. The phrases cover a range of pitches and each recital runs to thousands of notes. But complexity does not end there. No two songs of an individual sedge warbler are ever the same. The bird improvises a new programme every time he sings. But there is continuity. A sedge warbler always begins his song by quoting the last few phrases of his previous offering. He does so even after a long silent period. So what are all these notes for and why does the sedge warbler go to such trouble?
The scientist would say that long ago some female sedge warblers started using the quality of a male’s song as a measure of his suitability as a mate. Young sedge warblers then inherited a liking for singers from their mothers and a propensity to sing from their successful fathers. This in turn led to even more pressure on males to sing. Over countless generations, elaborate singing became the key to mate selection.
For an alternative, if rather muddled, perspective, read David Rothenberg’s Why Birds Sing, published by Allen Lane, 2005.