By ANNE BESTON
A New Zealand researcher has proved that fat birds sing better, providing an important clue as to why birds sing at dawn.
While studies suggest that in general birds sing to attract a mate and protect territory from rivals, the reason they do so at the start of
the day remains a mystery.
But research by Canterbury University zoologist Craig Barnett has found the more fat a bird has, the louder and longer it sings. The finding bolsters the theory that male birds singing loud and long at the beginning of the day are demonstrating to females their ability to successfully survive the night and, hopefully, boost their chances of finding a mate.
Because most birds don't feed after dark, they aim for a certain amount of weight gain during the day so they will survive until morning, even under the harshest conditions.
But birds experience the worst conditions only occasionally, leading scientists to speculate that they use up the excess energy by singing first thing in the morning.
Mr Barnett wanted to take the theory one step further and find out if that meant birds who had gained the most weight the day before, sang best. He carried out feeding trials on two native New Zealand species, silvereye and robin, using 12 birds of each species.
He measured daily weight gain and song output of the birds over three days and found they sang louder, longer and with a more complex song after getting extra food.
"Singing at dawn is such a mysterious behaviour but when females are looking for a mate, they want the best they can get and singing is one way they can assess the quality of the male," Mr Barnett said.
Scientists believe other reasons birds sing at dawn is because it is a good time to be heard.
Males may also sing at dawn to check which of their rivals have died overnight and therefore which vacant territory can be invaded.
Female birds are also at their most fertile at the start of the day so reproduction is more likely to be successful.
nzherald.co.nz/environment
