A charity team responded to every report of a swan stuck in an icy pond only to find it resting to conserve heat.

When we go into hot environments, our blood vessels dilate and come to the surface, while in colder conditions they constrict to conserve heat.

Callers said the swan's legs were trapped in the ice, but in fact they were simply tucked underneath it to conserve heat.

A group may roost in a tight circle with their heads pointed outwards to conserve heat and keep a look out for predators.

The same adaptations that conserve heat while in water tend to inhibit heat loss when out of water.