Millions of birds migrate from the UK to warmer climes each winter, some flying thousands of miles as far as sub-Saharan Africa or even Latin America in a journey that can take up to a month. Houses and other heated property is a favourite and any gap, nook or cavity will be occupied, resulting in many a household being woken in the night by the sound of birds scratching around in the eaves. Where do birds go in the winter?Ī final trick they employ is to find shelter: thick vegetation, a nest box, a hole in a tree, often huddling together for warmth. At night, they can then fluff themselves up and tuck their head under their wings for extra protection. These appear during the autumn moult and remain under the main body and flight feathers providing extra insulation (so good in fact, we still use them in pillows and duvets today) without adding excessive weight. Whilst birds cannot grow a thick winter coat (as many mammals do), they do add extra, light downy feathers. In fact, small birds can lose over 10% of their total body weight during a single winter night. So only small amounts of fat are stored, perhaps just enough to keep them warm for a single night. Unlike other animals they cannot afford to lay down extra fat as this would hamper their ability to fly and put them at risk of predation. While many of the dinosaurs from which they are descended were cold-blooded, birds as we know them are believed to have evolved into warm-blooded creatures many millions of years ago. Like humans, birds are warm blooded or endothermic, which means their bodies generate heat and maintain a constant temperature even in cold weather. But for those that don’t migrate, just how do they stay warm as we shiver through winter? Are birds warm or cold blooded? Even the comparatively mild UK loses many birds when the mercury drops. Of course, some birds escape the world’s colder regions entirely when winter rolls around, preferring to holiday in warmer climes. So how do birds, exposed to the elements all night and day, cope during the colder months? And when we step outside, we go equipped with coats, scarves, gloves, hats and all other manner of clothing. Even from the comfort of our centrally heated homes, wrapped up in cosy knitwear, we still feel the icy chill of winter.
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