A Northwoods Almanac for 1/6 – 19/2023
Chickadee Winter Survival
Saving energy is the key to survival for those relatively few birds who choose to remain here over the winter. Black-capped chickadees, weighing only a half an ounce, use a number of adaptations to get them through. Like many songbirds, they cope with freezing temperatures by fluffing out their feathers into an insulating puffball, a process called “pilo-erection.”
And like waterfowl, they allow their feet to remain near freezing by placing the artery that brings warm blood to their feet next to veins of cooled blood returning to their core. Heat is transferred between the outgoing and incoming veins, which allows chickadees to save a lot of energy regulating their temperature.
Chickadees also utilize winter nighttime roosting cavities. University of Alaska-Fairbanks biologist Susan Sharbaugh attached radio transmitters weighing less than 0.5 grams to some chickadees to discover where they roosted at night. One night she followed their beeping signals to a birch tree with a broken top, and the following day she watched a chickadee fly into a cavity the size of a quarter. Sharbaugh found other bird roosts, too, all of which were in birches, suggesting that birches provide the best nighttime quarters for roosting birds, at least in Alaska. Perhaps the waterproof and windproof bark provides the best insulation qualities, or a dying birch tree is most easily excavated. We’ve likely all noticed how a downed birch limb can be totally punky on the inside – perfect for easy drilling even by a little chickadee – while the outside bark remains perfectly intact.
Perhaps most important of all, chickadees go into a nightly regulated hypothermia, dropping their temperature 12 to 18 degrees below their normal daytime temperature of 108°F, providing a 25 percent decline in energy expenditure. That sounds fine except chickadees then have to shiver all night to keep warm, and they use up all the body fat they built up during the day, the equivalent of a 170-pound man spending a winter night outside and stepping on the scale in the morning 17 pounds lighter.
The next morning they have to gain as much as 10 percent of their body weight to replenish their body fat, eating twenty times more food than they do in summer (60% of their total body weight!).
Their need for so much food during winter has forced chickadees to become very efficient at finding food. They form flocks to forage together, sometimes with other species such as nuthatches, woodpeckers, and creepers. They not only seek seeds, but also invertebrates, including eggs and pupae, that are hidden in the ground or under bark.
Chickadees also store in autumn a vast number of seeds in hidden places and have the ability to remember the location of thousands of caches. They “scatter hoard,” stashing each item in a different spot. A single chickadee can store up to one thousand seeds a day, or eighty thousand a season! The remarkable memory needed to find all these seeds is possible because chickadees grow new neurons in late fall, while they are storing food. They also have the ability to discard cells that hold old memories and replace them with new cells.
And by the way, UW wildlife ecologist Margaret Clark Brittingham kept track of 576 black-capped chickadees in a winter study in the 1980s. Her research showed that during milder winter weather, chickadees that had been exposed to feeders as a supplemental food source did not become dependent on the feeder food, surviving at the same rate when the feeder food was removed as did chickadees that had never been exposed to feeder food.
On the other hand, however, Brittingham’s research did find that during harsh weather (below 10 degrees F), black-capped chickadees benefited from supplemental food they obtained at feeders. The survival rate of her subjects, compared to those birds that obtained less-accessible food from the wild during severe winters, nearly doubled when they consumed sunflower seeds at feeders.
So, if you can, be sure to feed chickadees during the really cold winter days and nights. However, if you want to go on a vacation but feel guilty that “your” birds are dependent on you and may not survive, see if you can choose some more moderate winter days and nights to be gone.
No matter what, though, remember that chickadees are masters at winter survival. Rest assured, some will find a way to survive.
Manitowish Waters Christmas Bird Count
We conducted our 30th annual Manitowish Waters Christmas Bird Count on 12/17. We did our best to cover a circular area with its center at the intersection of Hwy. 51 and Cty. W., and with a radius of 7.5 miles. For the most part, this is relatively wild woodlands and wetlands with few homes, so we tend to find relatively small numbers of birds compared to other more urban counts where bird feeders are frequent.
Still, between our 21 volunteers, we found 30 species, and 1,512 individuals. Most numerous, as always, were black-capped chickadees, with 391. Next in line, however, were two surprises. Second in total at 200 were bohemian waxwings, a Canadian species that only occasionally graces our area in winter. And just behind them in third were 173 evening grosbeaks, our highest total ever in our 30 years of counting.
Another surprise was the number of American tree sparrows we found – 30 – also, our highest number ever! Our previous high was 6. This species breeds in remote northern areas, often north of the treeline. I always think of them as ground feeders, foraging among weeds and grasses for seeds. So, given our deep snows, I expect them to migrate well south of here. But in researching them further, I’ve learned they also feed along branches and twigs, and will beat weeds with their wings and then fly to the snow surface to retrieve the seeds. Plus, they consume berries and catkins directly from trees and bushes up to 50 feet above the ground, and they readily feed on seeds from ground feeders. So, apparently I shouldn’t be as surprised by their presence as I am.
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| photo by Bev Engstrom |
Notable by their almost total absence were pine siskins and common redpolls, both of which were in good numbers last year.
Also notable was our failure to find a single gray (Canada) jay. We consistently found them from our first count in 1993 onward, but not anymore, last counting one in 2011. We’ve always been at the southern edge of their breeding range, but they are clearly receding north as our winters warm. A few are still seen now and again, but not with any consistency.
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| gray jay range map |
Finally, we continue to find wintering trumpeter swans on an open stretch of the Manitowish River, a phenomenon first observed on our count in 1999. Most trumpeters migrate, but a consistent band of a dozen or more choose to remain the winter here for reasons only they can explain.
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| photo by Jim Schumacher |
Celestial Events
The full moon (the “Wolf/Frost in the Teepee/Great Spirit” Moon) occurs tonight, 1/6. For planet viewing in January, the action is all after dusk. Look for brilliant Venus (-3.9 magnitude) low in the southwest, Mars (-0.9 magnitude) high in the east, Jupiter (-2.3 magnitude) high in the southwest, and Saturn (0.8 magnitude) low in the southwest.
Recall that a difference of 1 magnitude corresponds to a brightness factor of about 2.5 times. Thus a difference of 5 magnitudes corresponds to a brightness factor of a hundredfold (multiply 2.5 five consecutive times). So a 1st-magnitude star is 100 times brighter than a 6th-magnitude star. A difference of 10 magnitudes corresponds to a brightness factor of 10,000 times. Thus, Venus at nearly -4 magnitude is 10,000 times brighter than a 6th magnitude star, which are the faintest stars we can see with our naked eye.
Patridgeberry (Mitchella repens)
Several columns ago, I identified five species of northern plants that hold onto their bright red fruits over the winter – sumac, winter holly, partridgeberry, wintergreen, and highbush cranberry. Let’s look at partridgeberry, an unassuming, native perennial common throughout the forest understory of Eastern North America, ranging from Newfoundland to southern Florida and eastern Texas. Its glossy, dark green evergreen leaves hug the ground on stems that often spread into colonies and form a dense carpet on the forest floor.
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In spring and summer, small white tubular flowers grow in pairs along the stem. The flowers attracts a variety of pollinators, but most notably bumblebees. And here’s where partridgeberry does something I’m unaware of any other flower in our area doing. One flower in the pair has a short pistil and long stamens, while the other has a long pistil and short stamens, an adaptation that prevents self-fertilization. If both flowers in the pair are fertilized by bumblebees, the ovaries of both flowers fuse together to produce a single oval-shaped scarlet fruit with two dimples.
The two small depressions where the two flowers join led to the old common name of “two-eyed berry.”
The plant's generic name, Mitchella, was a nod by Linnaeus to Dr. John Mitchell, an 18th-century Philadelphia botanist and physician. The species name, repens, is derived from the Latin for “creeping.”
The tiny red fruit ripens by late summer, and can persist throughout the winter. The fruit may be consumed by ruffed grouse, turkey, fox, racoon, skunk, white-footed mouse, and white-tailed deer, though it doesn’t seem to be a favorite of anyone’s. The berries are edible for us, too, but I think they’re really bland.
Lots of folks are looking for native ground-layer landscaping plants, and the non-aggressive partridgeberry works really well for small areas. It’s best used in woodland, shade, or border gardens, or along paths and in rock gardens. It transplants well, and just a few cuttings will create a nice-sized evergreen mat.
Thought for the Week
“Every human has four endowments – self-awareness, conscience, independent will and creative imagination. These give us the ultimate human freedom … The power to choose, to respond, to change.” – Stephen Covey
Please share your outdoor sightings and thoughts: e-mail me at manitowish@centurytel.net, call 715-476-2828, snail-mail at 4245N State Highway 47, Mercer, WI, or see my blog at www.manitowishriver.blogspot.com.
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