Why are a large number of vultures bald?

For years, experts have assumed that vultures have bald heads and necks to prevent their feathers from being soiled when they tuck into a meal, usually a newly discovered carcass. That notion has helped fuel the perception of vultures as unsophisticated, blood-thirsty scavengers.

However, new research has proved that vultures may also sport the bare-faced look for a very different reason. They look that way to stay cool.

When it is cold, the vultures clearly hunch their bodies, tucking their heads in, and reducing the surface area through which they could lose heat. When it is hot, the birds stretch their necks out and open their wings in order to dump as much heat as possible.

By changing their posture to expose more or less of the bare skin on their heads and necks, vultures can cut their heat loss by half in cold conditions and increase their heat loss by almost a quarter in certain hot conditions.

Most other species of vultures, such as the American king vulture, sport bald heads and necks for the same reason, while other birds, such as emus, ostriches and cassowaries, that have either bald heads, or large areas of bare skin such as wattles, may also use them as 'thermal windows' that help control heat loss.