The dawn chorus created by some of our favourite songbirds could be changing because the birds are having to adapt to excessive noise levels, according to new research.
A study led by the Museo Nacional de Ciencias Naturales in Madrid measured noise at five airports in Europe: Berlin, Barcelona, Madrid, Valencia and Malaga.
They found that where aircraft noise overlapped with the usual time they start singing, birds of all species sang earlier. Indeed, the average time for the dawn chorus was 23.8 minutes earlier at these sites than elsewhere.
Robins, Blackbirds and Nightingales were among the species affected, while Blue Tits and Goldfinches began singing almost 30 minutes earlier than usual in order to avoid being drowned out by the ambient man-made noise.
Lead author Dr Diego Gil told the Sunday Telegraph: "Birds change their behaviour in anticipation of the increase in noise. An earlier dawn chorus is being seen in our cities too because of the joint effects of high ambient noise levels at dawn and continuous artificial lighting overnight."
The researchers warned in the journal Behavioural Ecology that too much noise could be making it difficult for birds to communicate with one another, but singing while it is still dark raises the risk of attracting attention from predators.
Furthermore, the birds may be at risk of reducing their energy levels, as they typically sing and then forage for food soon afterwards. If it is still dark, they will be unable to do this.
According to the RSPB, May and June are the peak times to enjoy the dawn chorus in Britain, especially days with little wind and fine, clear weather.
Different species choose different times to sing depending on when they need to breed and defend their territories, but warm spring and early summer weather tends to attract most species.
If a bird sings long into the season when its counterparts have stopped, it could be that this is a lone male bid that has failed to find a mate.