What makes mountain birds sing at dawn—and why are they sometimes quiet? Ecologists explain

Three species of the melodic African warbler bird refuse to get up early and sing their customary daybreak songs when the weather is cold. This new discovery was made recently by a team of soundscape ecologists in South Africa's mountainous Golden Gate Highlands National Park. The team's research co-leader, Mosikidi Toka, studies how animals and the environment make and use sounds, especially in mountains, and is currently completing a Ph.D. on the sounds of natural habitats. He deployed automated audio recorders to record the birdsong and find out how the birds were affected by freezing temperatures.