How does the robin stay warm in winter?
"The North Wind doth blow,
and we shall have snow,
and what will Poor Robin do then?
She'll go into the barn,
keep herself warm
and hide her head under her wing.
Given their beautiful red plumage it is not surprising that robins are the most recognised and possibly best loved of garden birds; there are almost as many robins as people in Ireland -- four million is the current estimate.
In fact, the robin was called the redbreast and the name robin was only officially accepted by ornithologists in the 1950s.
The bright red breast also gives us a clue as to how the bird can survive the winter. The only use that the robin makes of its redbreast is in display when defending its feeding territory against other robins.
In the spring breeding season, pairs of robins defend a territory but in the autumn and winter males and females defend separate territories in which they feed. The territory sizes vary depending on the habitat and season but in the breeding season they are about 0.5ha and in winter about half this size, i.e. an area of about 50m x 50m. In order to maximise its chances of getting enough food to survive the winter, the robin will defend its territory to the death and prevent other robins from feeding in it.
This is very important because small animals are particularly sensitive to the cold. A robin can lose as much as 10pc of its body weight to keep itself warm on a cold winter's night and its fat reserves will only keep it alive for a very short period. The availability of food is therefore critically important.
On a cold night the robin will take refuge in sheds or thick trees and tuck its head under its shoulder plumage -- just as the nursery rhyme tells us. The robin also puffs out its feathers so that they almost stand on end, trapping warm air pockets next to its internal organs. Air is an excellent insulator so even a few millimetres under the feathers will keep the robin's body temperature up.
If we get a white Christmas, the robin's outer feathers are cold and snow doesn't melt on cold feathers so our red-breasted friend stays warm.
Sometimes the robin stands on one leg and pulls the other up under its body to keep warm. It may also use its belly feathers to keep its feet warm.
However, consuming calories is essential for the bird to keep warm and the robin is extremely good at foraging. The friendly robin will follow gardeners to catch worms and will readily eat from bird tables and even from the hand in order to build up fat reserves that keep them going when the berries become scarce and the ground hard.
So as you get ready for Christmas, leave out some nuts and seeds for the robin and listen out for its powerful chirp.
QTom Bolger is Professor of Zoology, UCD School of Biology & Environmental Science