Over the past month I’ve really enjoyed watching all our lovely waders, ducks and geese get settled into their corner of the Solent as they arrive from their long migrations. They often look so comfortable and beautiful out on the chilly water or stood in frigid mud. Have you ever wondered how they are able to thrive in what can seem a harsh environment?
Birds have many fascinating adaptions to deal with frigid habitats. Some observable and obvious and others far more mysterious. Which brings me back to ducks. When it is cold, legs are a site of potential heat loss as they are not covered by insulating feathers. Therefore, ducks, gulls and other waterfowl employ something called a counter-current heat exchange system. This sounds complicated but it is quite clever and simple. The veins and arteries at the top of their legs are entwined together as if in an embrace. This simple blood vessel embrace allows for something amazing to happen. It works like this: The blood in the arteries traveling towards the feet is warm as it leaves the body, the blood in the veins travelling towards the heart is cold as it enters the body. The blood vessel embrace allows for heat to transfer from the arteries to the veins, and ta da!… blood going to the body is now warm and blood going to the feet is now cool. This simple system allows for 95% of heat to be retained. Additionally, heat loss can be halved if the bird chooses to stand on one leg while resting. Pretty amazing.
But not all birds have this adaptation as far as we know (and there is much we do not know). Our wading birds like the dunlin and oystercatcher use a variety of other techniques. We recently posted this video(Opens in a new window) showing a turnstone with its beak tucked under its shoulder feathers and its body appearing to increase in size like a small balloon. There are two fantastic heat loss adaptions at work there. The beak tucked away allows the bird to breath in warm air trapped in its feathers and the fluffing of the feathers creates air pockets for additional insulation; essentially they trap air, warm it and then keep it there like a warm blanket. Incidentally, this is one of the reasons why disturbing birds at rest can be so harmful. If a bird has fluffed and tucked but then is forced to walk or fly because a person or dog got a touch too close, it will lose all that lovely warm air trapped in its feathers and with it, the energy it took to create that warmth.
There are a myriad other adaptations birds use to regulate body temperature including oiling their feathers, sunning themselves and even nightly hibernation called Torpor where they drop their body temperature and reduce their metabolism significantly. We will save that for another blog as I am now in danger of going into full geek mode!
So next time you are out on coast tucked into your warm jacket and sipping a hot coco, remember how clever nature is at adapting to winter climates that you and me would find unbearable without our warm woollies on.