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Survival in the Cold by Design — Chickadee in Winter Snow

As I sit in my warm office in Michigan today, I look out at snow and ice. My outdoor thermometer registers -8 degrees, and I wonder how the ducks on the river, the squirrels on the ground, and the birds in the air handle these frigid temperatures. I enjoy watching the birds on my bird feeders and the squirrels chasing each other in the oak trees, but I wonder how they survive. Then I apply my knowledge of physics, and I understand animal survival in the cold.

I always enjoyed teaching the heat and thermodynamics section of my high school physics class. One of my lines that always got a laugh was, “Why do we need to wear clothes to survive, outside of the obvious one.” The point is that our skin is not very good insulation against the cold. In winter, we pick clothes with air spaces within the fabric because air is a very poor conductor of heat, so it insulates us from the cold. We use coats stuffed with goosedown or some facsimile to be well protected from the cold. Goosedown also insulates sleeping bags and quilts.

Chickadees visit my bird feeders regularly. They usually are relatively sleek birds that fly smoothly and efficiently. As I look at my chickadees on this day of -8 degrees, they are almost round. Their feathers are fluffed up to trap air, so the birds are well insulated for survival in the cold. They don’t fly as smoothly as they do in summer. They crowd my feeders and would sit there without moving if they could.

Squirrels have a different problem. Their coats give them some protection, but getting food is an issue when heavy snow covers everything. They need to keep warm but avoid activities that would sap their reserve of nutrition. My gaze goes to the top of the oak trees, and I see a large round ball of leaves and twigs. Many years ago, to expand our church parking lot, we had to take down a tree with a large round ball of leaves and twigs near the top. As the tree came down, a squirrel ran out of the ball. I put my hand into the nest to see what was inside. Even though the air temperature was 20 degrees, it was very warm inside the ball of leaves and squirrel hair.

God has equipped His creatures for survival in the cold, and His design enables our Michigan winter to throb with animal activity. Trial and error explanations are weak because survival errors are lethal. We can see design in the natural world that speaks of God’s wisdom and planning. The evidence allows us to “know there is a God through the things He has made” (Romans 1:20). Watching animals thrive in very cold conditions is an excellent example of that evidence.

If you have a bird feeder on your property, you are probably familiar with the amazing chickadees found throughout the United States, Canada, and Mexico. The six North American chickadee species do not have large fat reserves like some birds, such as finches. Instead, their trim size gives them more mobility to evade predators such as cats or sharp-shinned hawks. However, it also means chickadees must find enough fuel daily to maintain their metabolism.

One way chickadees survive is by lowering their body temperature at night. A chickadee’s daytime body temperature is 108 degrees Fahrenheit, but it drops to around 86 degrees at night. This controlled hypothermia is a nocturnal semi-hibernation that slows their metabolism by about 25%. The next day, they must find enough food to maintain their daytime metabolism while replacing fat lost the previous night.

Besides the seeds at our bird feeders, chickadees eat caterpillars, insects, spiders, and conifer seeds. Since chickadees don’t migrate south for the winter, they store food for use during the cold months. Their stockpiles exist in various places, such as wedged into pine needle clusters or tree bark or even pounded into the ground. They store food in the lower branches of conifer trees, so it will be available when the upper branches are covered with snow. Chickadees prepare insects for storage by removing the heads of larvae and the wings of moths.

Storing food for later use requires remembering where it is, and studies have shown that chickadees can remember where they stored items for months. The hippocampus is the area of the brain involved in memory and spatial learning. In the fall, when food storage moves into high gear, the chickadee brain grows new neurons in the hippocampus. Their brain stores visual cues such as the spatial relationship between significant landmarks, allowing them to remember their cache locations from fall until the following spring.

Those of us who maintain bird feeders frequented by chickadees notice that they are not as shy around people as most birds are. The complexity of the amazing chickadees is extraordinary. They are another example of God’s design in the natural world, enabling the survival of a small creature we take for granted. This design speaks eloquently of the fact that we “can know there is a God through the things He has made” (Romans 1:20).

Reference: National Wildlife magazine February/March 1998, pages 24 -28.

Tag: chickadee

Survival in the Cold by Design

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