I captured this late afternoon scene yesterday while walking the dog. All I had was my iphone and it didn’t exactly capture what my eye did. I edited the image using Efex Color Pro and Lightroom to return some of the vibrant blues of late afternoon winter to the shot that my eyes witnessed.
Today, after a 14-month review, the U.S. Fish and Wildlife Service listed the rufa subspecies of the red knot as threatened.
I captured this shot at the end of a winter storm a few days ago with my iPhone. The dark trees contrasting with the fresh white snow caught my eye. I developed this as a black and white in Silver Efex Pro.
Weighing less than a nickel and not much larger than your thumb, golden-crowned kinglets are the smallest birds to winter in the New England woods. How does a bird this small stay alive during the long and cold winter night?
Larger animals have a lower surface-to-volume ratio than smaller animals. As a result, they radiate less body heat per unit of mass and are therefore able to stay warm using less energy. In 1847, Karl Bergmann, a German biologist, used this principle to show that within most warm-blooded species, body mass increases with latitude and colder climates.
Kinglets are tiny; their small size seems to break Bergmann’s rule.
To make kinglets even more odd, they only eat insects, even in winter. You’ll never see one at your bird feeder. Nuthatches and chickadees – two of our other small, over-wintering songbirds – eat insects, but they also eat seeds and suet, which are higher in fat and calories than insects. Most insectivorous birds of the North Woods, of course, avoid the problem of staying warm altogether by heading south when insects become scarce. Not kinglets.
Birds generally need to maintain a core body temperature of around 104ºF, year-round. This high temperature allows for powered flight and quick movements and reflexes. But this high temperature also requires a large amount of fuel.
Bernd Heinrich, Professor Emeritus at the University of Vermont, wondered what kinglets were eating during the winter to keep the metabolic flame burning. He found that although they are fairly opportunistic, eating everything from spiders to insect eggs, they subsist primarily on moth caterpillars found over-wintering on trees. He collected some of the caterpillars and kept them in his freezer for the rest of the winter. In the spring, he took them out and thawed them, then raised them to adulthood so that they could be identified more readily. They turned out to be one-spotted variants, a well-known moth whose over-wintering location had not previously been known.
But this was only half the story. Researchers in Virginia calculated that kinglets could only build up enough fat during a day of foraging to fuel their metabolism for half the night. Even with their ability to find plenty of insect food in the seemingly sterile winter woods, they would be unable to stay warm throughout the night based solely on their daytime diet.
Several biologists had suggested that kinglets survive by sleeping in shelters such as old squirrel or bird nests or by huddling together. Enter the ever-inquisitive Heinrich once again. After dozens of attempts to follow kinglets foraging just before darkness fell, one December evening he was finally successful.
Heinrich reported his observation in the Wilson Bulletin, a journal of ornithology. “At 4:20 P.M. I saw three kinglets fly into a brushy white pine. In less than a minute, I found four kinglets huddled together about four meters above the ground under thick branches.”
He returned an hour later with a stepladder and a camera. The birds remained huddled together through the night with their heads tucked into their back feathers and just their tails sticking out of the feathery fluff. The temperature that night dropped to just 14ºF.
Kinglets, like other northern birds, are also able to recapture heat that would otherwise be lost through the skin of their non-feathered legs and feet. In addition to simply tucking their extremities into their thick body feathers while sleeping, birds have a vascular system in which arteries carrying warm blood out to the legs are located close to veins carrying the cool blood back to the body, allowing heat to be retained. The design is so effective that we humans use similar, artificial heat exchangers to recapture heat in all sorts of applications.
Heinrich also found that sleeping kinglets fluff up their feathers to make an inch-thick, downy blanket. His experiments showed that without this down comforter, a naked kinglet would cool 250 times faster than one fully feathered. He weighed the wing and tail feathers, which are primarily used for flying, and compared them to the weight of the body feathers, which are primarily used for insulation. Kinglets have four times more feather mass committed to insulation than to flying.
The smallest winter bird in the North Woods thus transforms itself into a much bigger bird each night, thereby creating a lower surface-to-volume ratio. Puffed-up and cuddling kinglets radiate less body heat per unit of mass, enabling them to conserve energy and survive the long and frosty New England nights.
This article appeared in Rutland Magazine. winter 2014
November at dusk with the temperature barely breaking 40 degrees I could see my breath. Yet, all around me moths fluttered through the woods. They were one of two species in the genus Operophtera, visually drab, but physically magical.
Whether these were the native Bruce Spanworm (O. bruceata) or the introduced Winter Moth (O. brumata), devilishly hard to identify by photograph alone, I couldn’t discern. Either way, both of these small, cold weather moths are thermo-conformers. Incredibly, they can fly with air and body temperature ranging from just 27 up to a balmy 77 degrees. Continue reading →
Each fall day he appeared with a skinny face and left with ballooned cheeks. Over and over he filled his cheeks and ran away to empty them. Our eastern chipmunk was living the good life. There was an endless supply of sunflower seeds spilling from the bird feeders.
Impossible to count as he gathered them, I wondered how many seeds he carried on each trip. University of Vermont biologist, Bernd Heinrich, pondered the same question. He found that he could insert 60 sunflower seeds into one cheek of a road-killed specimen, about a heaping tablespoon worth. Continue reading →
In the spring Spotted Salamanders crawl to vernal pools, temporary woodland ponds that fill with water but then dry out later in the summer and provide a fishless environment for larval salamanders, where they mate and lay eggs. But for 90% of the year they are somewhere in the forest. Sometimes you can find them by flipping over a large stone or rolling a rotting log, but for the most part, they are impossible to find. Continue reading →