It’s simple physics. In a cold environment, small objects lose heat at a faster rate than large objects. This is why most warm-blooded animals that reside in a northern climate tend to be large in size. Yet, for every rule, there is always an exception and when considering birds, the golden-crowned kinglet is a perplexing anomaly.
The golden-crowned kinglet is the smallest perching bird to inhabit the Adirondacks, as this delicate, olive colored creature is not much larger than a hummingbird, (which is classified in a group that is related to the swifts rather than the perching birds.) However, unlike our other small birds, like the warblers, vireos and wrens, the kinglet often remains in the Adirondacks throughout the dead of winter, traveling in small, loosely knit flocks in dense evergreen forests.
The yellowish-green plumage of the golden-crowned kinglet makes this tiny bird a challenge to see against the backdrop of pine, spruce, fir and cedar boughs as it flits through the canopy in a constant search for food. Yet because the kinglet frequently emits an audible “teez, teez, teez” call as it forages, its presence can be easily noted by a perceptive individual, especially at this time of year, when the sound of the wind through the branches is the only noise that breaks the silence of the deep woods.
Adding to the challenge of seeing a golden-crowned kinglet is its reluctance to take food from a feeder. This tiny bird feeds almost entirely on dormant bugs, clusters of invertebrate eggs, and caterpillars that overwinter on the needles and at the end of conifer twigs. However, unlike a woodpecker, the kinglet displays no desire to take advantage of a chunk of suet placed on a trunk or limb of a softwood tree.
This refusal to utilize a highly caloric source of food, like suet, seems counterintuitive for a creature that requires incredible amounts of food energy to remain alive during this season. It is estimated by bio-physicists that a golden-crowned kinglet needs to consume at least 2 to 3 times its own body weight in high energy nutrients, like fats, every day in order to maintain a normal internal temperature of nearly 110 degrees. Because of the rate at which a kinglet dissipates thermal energy, it must ingest a substantial amount of food every hour to avoid hypothermia.
While survival during the short days of winter when it forages for food is one thing, the lengthy nights are a different story. Some researchers have suggested that the kinglet extends its feeding activities through the periods of twilight, which shortens the duration of time it must endure its nightly fast. Others have indicated that the kinglet, like the chickadee, lapses into a period of torpor in which its body temperature drops significantly after reaching its roost. A lower internal temperature reduces the rate at which heat dissipates to the surroundings, and extends for several hours the temporary food reserves in its body. The idea that the kinglet may retreat into a nook or cranny, such as those that occur within a brush pile on the ground or inside an abandoned woodpecker cavity deep within the trunk of a tree has also been proposed.
Roosting in a place out of the wind, and where the air may remain a dozen degrees above the outside atmosphere, can help this bird greatly in conserving body heat. Also the notion that two or more kinglets may huddle together in a sheltered location has been proposed, as this would reduce the rate at which a body loses heat to the surroundings and would improve their chances of fending off hypothermia.
While all of these strategies for survival at night make sense, researchers have very limited evidence to verify any of these for this bird. One of the leading authorities on the golden-crowned kinglet in winter is Bernd Heinrich, a professor at the University of Vermont. He has been researching this tiny feathered creature for years and has found that his subject is very reluctant to reveal any of its secrets concerning how it deals with winters, especially at night. Heinrich has noted that most individuals do perish during winter in a northern climate, yet their exceedingly high reproductive rate compensates for these losses.
Over the past decade, the population of golden-crowned kinglets has grown in most of its range. This may be the result of the influence of global warming, which has shortened the duration, and decreased the intensity of the winter season. This is why it is more likely to hear the delicate “teez-teez-teez” call of the golden-crowned kinglet while out hiking, skiing or snowshoeing through an evergreen thicket this winter here in the Adirondacks.
Photo of golden-crowned kinglet courtesy Wikimedia user Snowmanradio.
A version of this article first appeared on the Adirondack Almanack in December, 2012.