It’s still dark, but the dawn chorus is in full swing. This performance, however – except for a thin descant of robin – comprises a single thrush species. Elsewhere, song thrush (Turdus philomelos) or mistle thrush (Turdus viscivorus) would be joining in by now, but around this urban garden, the blackbird (Turdus merula) commands the stage. Although their ancestors were shy forest creatures, since the 19th century there has been widespread movement of blackbirds into cities. Their population densities are now higher in urban environments than in the countryside. Increased competition for territory rouses more urgent strains, but they can’t override the melody. Blackbird song has inspired writers, musicians and composers, and here in Belfast there is a long tradition of enthralment. The local poets Seamus Heaney and Ciaran Carson paid homage with translations of the ninth-century Irish poem The Blackbird of Belfast Lough. Farther afield, the Welsh poet-priest RS Thomas meditated on “a slow singer … loading each phrase / With history’s overtones, love, joy / And grief …” (A Blackbird Singing). And as he was dying, the Swedish writer Henning Mankell movingly declared: “I have heard the blackbird. I have lived.” Despite their song’s emotional resonance for us, blackbirds are, of course, singing for their own ends – any overtones of history are strictly theirs. The songs of species which evolved in forests often sound musical to our ears. Where a voice faces physical obstruction, such as branches and foliage, pure tones transmit more effectively. The blackbird’s gorgeous motif is an adaptation to that circumstance, to ensure his fluting announcement can be clearly heard beyond his territory’s boundary. I tune into the cadence of the nearest bird. At the end of each verse, his mellow notes segue to a more scratchy twitter. After the mellifluous opening, this refrain sounds oddly dissonant. Its higher pitch carries poorly over distance; and its complex modulations are easily distorted by bouncing off surfaces. However, in both art and evolution, form follows function. This twitter is deliberately intended for his more immediate surroundings, to either warn or wheedle. Any rustle in the understorey could be an appraising male – or a prospecting female. Minutes before sunrise, sparrows start gossiping. The blackbirds fade to silence. A starling sneers.