Why don’t high-flying birds freeze in the frigid temperatures?

Birds fly at tens of thousands of metres high. Ice forms on the wings of planes at this altitude, so why don’t the birds freeze?

Lucy Hawkes, University of Exeter, Devon, UK

Birds can sometimes reach astonishingly high altitudes. The record is a massive 11,278 metres by a Rüppell’s vulture that collided with an aircraft. The resulting “snarge” – that is to say, the bird’s remains – left on the plane provided robust evidence.

Birds almost certainly don’t experience icing while flying at altitude for three reasons.

First, birds normally maintain their body temperature at about 40 to 41°C,…