When Aussie birds stop singing

Mick Roderick, BirdLife Australia. Professor in Animal Behaviour Gisela Kaplan says when the temperature rises birds generally stop vocalising to save energy. "When it comes to 40 degrees their breathing rate increases sharply — it then doubles — and from then on every single degree doubles the number of breaths the bird has to take. So, at 40 degrees it has 100 breaths per minute and at 41 degrees it's 200 breaths per minute. They won't vocalise once it gets to 40 degrees. When you get to 46 degrees that's the absolute limit and after that birds really suffer immensely, she said. Source: ABC News