Q: Why are birds so noisy at first light and then suddenly quiet?
A: In the hours around dawn, individual birds announce their ownership of territory to rivals and advertise to attract mates, said Greg Budney, curator for collections development at the Macaulay Library of the Cornell Lab of Ornithology.
As the morning grows lighter, birds turn to foraging for food for themselves and, if eggs have hatched, for their young and mates.
In many species, Budney said, the predawn chorus is specifically about territoriality or male rivalry; at dawn, male birds switch to a song aimed at attracting a mate.
At temperate latitudes, males do most of the singing, with the females undoubtedly listening. "It is the females that determine which male will successfully mate," Budney said. There is an evening chorus as well, just before sunset.
Because so many individuals raise their voices at once, researchers have found it difficult to tease out the exact content of the dawn chorus.
In 2004, Cornell scientists used an array of microphones and computers to track and separate the songs of four male banded wrens in Costa Rica. They found patterns in which males directed calls to specific neighbors and then responded to them.
The birds engaged in aggressive "song matching," essentially saying, "Anything you can sing, I can sing louder, because this is my territory."
A single song spreading in rippling patterns offered the first evidence of network-like communication during the dawn chorus, the researchers said.
ActiveStyle on 08/24/2015