On the fourth day...The Changing Sound of Birds’ song
Fri, 04 Dec 2015 11:04:00 GMT
The four calling, or colly birds, given as presents on the fourth day of Christmas should remind us of Rachel Carson and her seminal work on the impact of pesticides on birdsong. Writing in the 1960s Carson drew the world’s attention to the demise of singing birds as a result of intensive agricultural production, resulting in what she called a Silent Spring.
Fifty years later, fortunately we still can hear blackbirds singing (they were the ‘colly’ birds of the original Twelve Days of Christmas). But will global warming change all that?
Climate change has meant that many birds around the world are having to shift their migratory habits. This means that they are pitching up in places that they have not traditionally visited – causing great excitement of course for the ‘twitchers’ amongst us. One consequence of this is that birds adapt their songs to their new surroundings. For example, in noisier environments it is more difficult for birds to make themselves heard and researchers have found that urban birds are shifting their songs up a pitch. But before we get excited about the idea of cities having louder dawn choruses than country villages, there are other concerns. Because a lot of bird species are beginning to coevolve with each other they are having to try harder to differentiate themselves. This could mean that their songs start to change. That might not seem too bad – after all we all love to hear new songs, but in the bird world music really is the food of love.
Botero of the National Evolutionary Synthesis Centre in Durham, North Carolina, an expert on how climate influences sexual selection in mockingbirds, argues thatthe choices made by female birds drive the evolution of male birdsong, but that these varied under different climatic circumstances. In mild, stable climates the males don’t have to worry too much about their singing in order to attract the ladies. But once the climate gets more tricky and unpredictable, the females get a lot more choosy – and the males have to up their game. Botero suggests that this is because birdsong requires a lot of brain power and that more tuneful males are demonstrating their superior intellect in order to attract females, who want cleverer mates to help them navigate the challenging environment.
So - as our environments get more chaotic can we look forward to the sound of joyful trilling from the alpha males? Maybe - but at a cost - ‘use what talents you possess, the woods would be very silent if no birds sang except those that sang best’!
