A Nagoya University study found that birds start singing in the spring when the days are what?
Why do birds sing? Ornithologists have learned that the longer hours of light that come with spring trigger the release of hormones in birds. These hormones prompt the enlargement of the birds’ gonads which, in turn, stimulate male birds to sing.
linked to hormones
A group of researchers has discovered a hormone that sets off neural activity that causes birds to sing when the days get longer.