How Do Birds Survive the Cold?                                                                                

With short days and long nights, the life of birds in winter is not as care-free as people would like to think.  At this time of year, often someone comes in and says they saw the fattest little birds at their feeders.  “They must really be eating to get that fat”.  I’ve seen them at my feeders and they look like they’ve swallowed a ping pong ball. What we are observing is a cold little bird, which has the ability to fluff their feathers to create air pockets for additional insulation in the winter.  They can actually increase their heat retention by 30%.   

While about 75% of the bird population migrates,  of the ones that stay with us several bird species actually grow extra feathers, which are light in weight for the purpose of flight, as part of the fall molt.  For example a chickadee has about 1,000 feathers in the  summer and 2,000 in the winter.   Also the oil that  “coats” their feathers is used for insulation.   Their legs and feet are also covered with specialized scales that help them minimize heat loss, and they have little fleshy muscle and relatively few nerve endings in their feet, thus they don’t often freeze to feeders.  They may  occasionally lose a toe or even an entire foot, but observers note this is very rare. Some birds may enter a state known as “torpor” a.k.a. purposeful hypothermia, to conserve energy during cold winter nights.  This can be very dangerous as their reduced temperature also reduces their reaction time to predators.

Birds are warm-blooded animals and they have a much higher metabolism and higher body temperature than humans.   Body temperature (on average at 105°) can fluctuate during the day depending on the climate and the amount of activity, but it can be a very big challenge for them to maintain the needed high body heat. On sunny days we often observe birds with their backs turned to the sun (therefore exposing the largest surface of their bodies to heat).  Birds are also known to roost together and crowd into small tight spaces to share body heat.  Bird houses and roost boxes are popular locations in the coldest of weather.   

Have you noticed a bird shivering, a.k.a. thermogenosis”.   Actually, they are shivering to raise their metabolic rate and generate more body heat.  It is an effective way to stay warm, although it requires more calories.   Often seen standing on one leg, while the other one is tucked into their warm plumage, and sleeping with their bills and face tucked, with just one eye open, they are preserving body heat.  Can you imagine what we would look like after standing or sitting several hours out in this kind of weather?   My husband freezes just looking out the window, much less out in the snow.   

What can we do to help them?  Those bushes and shrubs that we tire of tending through the summer can provide a wind block that most species will take advantage of and a necessary place to hide from predators.  If you have a tree area that has some fallen limbs, be sure to leave this during the winter as cover for the birds. 

All birds can build up some fat reserves to serve as insulation and extra energy for generating body heat, and this is why many birds gorge during the fall when food sources are abundant.  This gives them an extra fatty layer when winter arrives.   We can all contribute to their survival by feeding quality, high in fat foods, such as suet or black oil, which are high in protein.  Also, keeping water available in a heated or solar birdbath is a must, as eating snow only depletes their body temperature even more.  With all the joy they give us, they are truly worth the extra effort.   If you don’t have a feeder near a window you frequent, that’s a great Christmas gift to ask for.

 Happy Bird Watching