What is most important?
Calories, and burning them, are the best way to body warmth in winter for birds, so you can see how our feeder feeding helps in this area with high calorie seed and suet. Birds have other tricks under their wings to help as well. Let’s investigate…
Do you know how much of keeping warm is dependent on bird attire? Just like us, they put on their coat and boots’ so to speak.
- They have independent ‘thermostats’ for their extremities, like legs, and their core. If we did, mom would not have to hound the kids on putting on the galoshes.
- Their tiny, tooth pick legs are covered in scales which insulate and help to keep the bird dry. It is surmised that scales, not being living tissue similar to our hair and fingernails, do not get frost-bitten, yet cover skin that does. But if you notice a bird squatting over its legs on its perch, that means it is really cold.
Did you know that Mourning Doves have lost toes to frostbite? That is because they have not lived in cold areas as long as tougher birds like chickadees, and have not yet adapted to colder regions.
- Birds seek shelter in densely branched plants. Conifers are especially important for keeping birds dry and out of blistering winter winds. But they also provide food in the form of nuts and seed from cones – berries in the case of a plant like Juniper, cedar or cypress. Kind of like our bed and breakfast lodgings, huh? Many of these native plants provide shelter and a food source in winter, keeping birds warm inside and out. Safe from predators too!
- Feathers have an oily coating that helps to insulate and keep the bird dry. All weather jacket?
- They molt in Fall which will grow in the new set of feathers thicker and more numerous, further insulating the bird.
- They fluff the feathers to add a layer of insulating air. Think our layering of clothes to keep warm. It adds pockets of air too.
- Birds have a feast in Fall to bulk up before winter, adding excess weight and build layers of fat. Thanksgiving dinner?
- They shiver like us, but when they do, use their flight muscles.
- Some roost in clusters in tree cavities to share body heat. They also use conifers for gathering.
- They face away from the sun to expose the largest surface area to the warming rays, often spreading their wings too.
Scientists have found…
Birds like chickadees take staying warm a bit further by entering a state of torpor to stay cozy during severely cold winter nights. During torpor, the body temperature may drop between 10 to 15 degrees, but could be as much as 50 degrees. Their metabolism slows down to conserve energy in a state called nocturnal hypothermia. Torpor is like a deep sleep that lowers heart rate. This saves a bird up to 20 percent of conserved energy.
Birds regulate their body temperature through metabolic heat production which means balancing the intake of energy with what they have eaten. They also reduce heat loss through their unique circulatory system of arteries and veins.
In many birds, arteries and veins in their legs lie in contact with or adjacent to each other in order to exchange heat and maintain temperature. Arterial blood is usually at body temperature when sent to the feet and runs along side the cooler returning blood in veins. This unique circulatory system keeps warm blood of arteries warming the returning cooler blood of the veins. It also helps explain their differing ‘thermostats’.
Bigger is better, but not always…
Typically larger birds deal better in cold weather than smaller birds, doves, as I noted above not being as adapted to cold, and the walnut sized chickadees that enter torpor to conserve energy, as an exception.
Have you ever noticed that birds who winter in cold regions are generally larger than their relatives who live in warmer regions? It allows them to conserve body heat more efficiently since producing that heat is a costly endeavor to the birds. It is no surprise that the Common Raven, Corvus corax, or the Blue Jay, Cyanocitta cristata, also a passerine bird in the family Corvidae, fly the skies here in the cold north.
Upcoming is interesting, important and gets YOU involved…
The first post in this series was on backyard feeding, entitled, So How Beneficial is Feeding Backyard Birds? . It looked at the pros and cons of the wildly popular hobby shared by 65 million US residents. I hope you are enjoying this series and maybe, learning something you didn’t know. The next post has things that you might find interesting too.
My next post in this series deals with disappearing sparrows. Although not attributed to loss from winter, they are facing a mysterious loss of population. I propose some theories myself.
How about you, can you add to the discussion with your hypotheses? It is a post to see if we as gardeners can help identify reasons why sparrows are in decline worldwide. I will tabulate your ideas and post them on March 20th, World Sparrow Day. Maybe we can help scientists look in new directions. After all, our ideas come via a wide world too!
Also, sparrows are beautifully featured, not something many do for this common bird which pesters our landscapes. I made them as pretty as the cardinals that visit, at least in my opinion. Hope you think so too.
Then a post for those not faint of heart. I follow a hawk around on his hunt. The drama unfolds in the wintry landscape, but does not play out as you might think.