How do small birds survive in the middle of winter?
Birds have a warmer body temperature than humans – 40 degrees compared with our 38 – so we would think they feel the cold more than we do, and that they would have to work harder to maintain that temperature.
Small birds survive surprisingly well in cold conditions. They seek out sheltered places and take advantage of any milder breaks, but they need to keep busy seeking food.
Feathers are effective insulators. Well-oiled feathers protect from water. Sometimes we see birds “fluffed up” in winter – as in today’s photo of a winter male blue wren (fairy-wren). It has trapped a layer of insulating air between its feathers, helping to conserve body heat.
Most birds can restrict blood flow to their legs and feet, thus reducing heat loss.
Also, most birds add to their fat reserves before winter too, providing not only another layer of insulation, but also a reserve of energy.
Like us, they seek out sunny places to take advantage of solar heat; we often see birds perching to catch the sunlight early on frosty mornings.
A few birds enter a sort of torpor during the cold conditions, further reducing their body temperature and thus requiring less energy.
A Castlemaine resident reports red-browed finches – perhaps in some degree of torpor – not moving away as normal when approached in cold weather.
A lot of small birds simply move north before the worst of the winter weather arrives, but quite a number remain. Treecreepers, robins, wrens, sparrows, goldfinches and thornbills are examples. Even a percentage of the swallow population stays here to somehow find flying insects during winter.
The flame robin defies logic and comes out of the forest in winter to spend the coldest months in open country with very little shelter.
Small birds such as tits, sparrows and others survive the snowy winters of the northern hemisphere.
Today’s photo, taken in July, shows the first traces of blue appearing on the wren’s crown, as well as the blue tail – both signs of a male in winter plumage, starting to regain his resplendent springtime blue.
A female would be slightly browner, with a brown tail and a reddish beak.
A note last week mentioned the sighting of the season’s first swan nests at Lake Wendouree.
One pair of swans obviously nested out of sight and have already produced their three cygnets, first reported last Monday.
These are the first young birds of any sort reported so far this season.