THE KINGLETS’ KEY - Winter World: The Ingenuity of Animal Survival - Bernd Heinrich

Winter World: The Ingenuity of Animal Survival - Bernd Heinrich (2003)

THE KINGLETS’ KEY?

Kinglets are small, beautiful, and pure in their simplicity. They remind me of snow crystals. Each snow crystal is a six-cornered starlet formed according to the unvarying laws of physics and chemistry. Each one is perfect. Yet the diversity in their shapes is astounding in part because any tiny random event in their formation shapes all future events in their growth.

Similarly, in the evolution of organisms and ecosystems there are innumerable random events of history that shape outcome. Outcome is not preordained. There are no correcting factors or laws from above that specify the form of the ultimate outcome, even as the shape of the kinglets’ adaptations necessarily conforms to energy economy of life just as the snow crystals’ shape conforms to the blind energy economy of physics. Ultimately, the kinglet is to a snapping turtle, or a crossbill, or an arctic ground squirrel, or to us, as one snow crystal is to another. But to appreciate that fact requires seeing them up close.

I made my first attempt to catch a kinglet in my hand when I was about nine years old, and I remember the occasion clearly. It was in the late fall, and I was alone, walking along a woods road back from the village school, when I encountered a small group of them foraging close to the ground among some young spruce trees. I got almost close enough to touch them. They seemed oblivious to me, and I reached out to try to capture one. I did not succeed, but they had captured my imagination, as they have many others’.

In the introduction to the golden-crowned kinglet chapter in his now truly classic multivolume Life Histories, a standard reference text on North American birds, Arthur Cleveland Bent wrote: “Many years ago, a boy found on the doorstep the body of a tiny feathered gem. Perhaps the cat had left it there, but, as it was a bitter, cold morning in midwinter, it is more likely that it had perished with the cold and hunger. He picked it up and was entranced with the delicate beauty of its soft olive colors and with its crown of brilliant orange and gold, which glowed like a ball of fire. In his eagerness to preserve it, he attempted to make his first birdskin. It made a sorry-looking specimen, but it was the beginning of a life-long interest in birds, which lasted for half a century.”

Kinglets are named Regulus (“little king”) for their bright lemon yellow, orange, and red crowns. In the golden-crowned kinglet (Regulus satrapa), the females’ crown is yellow and the males have an orange-red crest of feathers within the yellow crown that is usually hidden out of sight, but it is raised like a flickering flame to show excitement.

Taxonomically, kinglets have long been a puzzle. Bent placed them among the thrushes and their allies. They have also been assigned to the titmice family, Paridae. They were thought closely related to the Old World warblers, subfamily Sylviinae (as opposed to the New World warblers, Parulidae). However, DNA studies (Sibley and Ahlquist 1985) suggest that they are of another descent (Ingold and Galati 1997); they are now known to be unrelated to either thrushes, tits, or warblers (Sheldon and Gill 1996). They are different, and unique.

In Europe there are two species of kinglets, the goldcrest Regulus regulus and the firecrest Regulus ignicapillus. Both species are relatively sedentary, but not entirely so as they have a tendency to migrate north and south within Europe. In North America there are also two species of kinglets. The ruby-crowned kinglet (Regulus calendula) breeds in Alaska and throughout Canada and migrates in the winter to Mexico and the southern United States. In contrast, the golden-crowned Regulus satrapa occurs throughout the United States and southern Canada in winter and summer, although part of the population also migrates into northern Canada to breed there.

Despite the depictions in most bird books, recent studies of the kinglet’s proteins (Ingold, Weight, and Guttman 1988) indicate that there are substantial genetic differences between the two American species. These differences are large enough to warrant putting them into different genera. On the other hand, our North American golden-crowned kinglets are nearly indistinguishable from the European and Asiatic goldcrest. Even their songs are nearly identical (Desfayes 1965). They could easily be lumped into the same species, although for perhaps no other than practical purposes they currently aren’t. For practical purposes I also restrict my discussion to the North American golden-crowned kinglet.

The golden-crowned kinglet’s ability to hold on in the north, where insect food is plentiful in summer and scarce in winter, is in no small measure dependent on its nesting behavior. Kinglets produce many young that compensate not so much for a high nestling mortality as in most other northern songbirds, but for a high winter mortality. Their nesting behavior is noteworthy in several ways. First, even in Maine and in Nova Scotia, where the deciduous trees don’t leaf out until mid-May, the kinglets already start nest-building in mid-April. Snowstorms are still common at that time and if kinglets built their nests like many other birds, then these nests would often be buried under snow. However, unlike crossbills, kinglets build their nests suspended under spruce branches where they are covered from above by a thick latticework of twigs and needles. Here the nest is virtually invisible from above and therefore well protected from most predators, and if the branches over a nest get covered with a thick layer of snow then all the better, because the nest is then inside a snug insulating snow cave.

Cold is still a potential problem early in the year, but a kinglet’s nest is built for warmth. Few people have observed the nest-building process, and even fewer have described it. I quote here a detailed set of observations of Miss Cordelia J. Stanwood, of Ellsworth, Maine, whose notes were published by Bent (1964, p. 386):

Golden-crowned kinglet beginning to build a nest.

The kinglets selected for the roof of their cradle a heavy spruce limb with a dense tip; and the female, hopping down through the branch from twig to twig, attached her pensile nest to the sprays.

The bird wove her spherical structure about herself much as the caterpillar of the luna or cecropia moth weaves its cocoon about itself, except that the kinglet had to gather her materials. The bird stood on a twig on one side of the space she had chosen for her nest and measured off her length, as far as the situation of the twigs would permit, by attaching bits of spider’s silk and moss to the twigs. Thus she laid off the points for the approximate circle for the top of the nest. Then she spanned the space through the center of the circle, roughly speaking from north to south, with spider’s silk and moss, forming a sort of cable, which later assumed the appearance of a hammock. After a time, when the bird came with moss or silk, she would fly down upon the hammock as if to test its strength and lengthen it. At all times, however, she worked all over the nest from left to right, moving her beak back and forth as she secured the silk and moss and stretched the web from one point of attachment to another. As soon as the hammock would support the bird, she stood in the center and walked around from left to right. When the hammock was wide enough to admit of her sitting down, she modeled the center of the suspended band by burrowing against it with her breast, and making a kicking motion with her feet. Gradually she embodied some of the twigs in the structure, as if for ribs, and occasionally she snipped off a spruce twig to use in shaping the globular nest. At last the bottom, or basketlike part, arose to meet the top of the nest and the industrious goldcrest was hidden from sight as she labored.

The creation was really a silken cocoon, in the walls of which was suspended enough moss, hair, and feathers to render it a non-conductor of heat, cold, and moisture. This primitive incubator was made of the same fine, dark yellow-green moss, Hypnum uncinatum, that seems characteristic of the habitations of the golden-crowned kinglet in this locality, Usnea longissima, a long, fringelike lichen, and animal silk. More of the gray-green Usnea lichen was used in the hammocklike band around the middle of the nest than in other parts of the well-made structure. The lining consisted of rabbit hair, I think, and partridge feathers. The wall of the abode was all of an inch and a half thick, and the window in the roof measured an inch and a half in diameter.

Apparently the female alone builds the nest. The male accompanies her and sings as she gathers nesting material and builds. Bent (1964) provides descriptions of other golden-crowned kinglets’ nests from the Northeast, and he documents the birds’ habit of lining the nests with feathers. Ruffed grouse (“partridge”) feathers appear to be used in almost all nests. The breast and body feathers of grouse are of course rather huge for the small kinglet’s nest, but the birds insert these feathers into their nest lining so that the quills point down into the bottom of the nest and the natural curve of the feather reaches over the top, forming a soft flexible curtainlike cover.

The majority of songbirds breeding in New England have four to five eggs per clutch. Kinglets have a whopping eight to eleven in a single clutch. They lay so many eggs and their nests are so small that, unlike other birds, the eggs are in two layers, usually five on the bottom and four on top. The bee-sized kinglet hatchlings are pink, blind, and naked. Stanwood (in Bent 1964, p. 388), in describing the young, says:

A kinglet incubating all of its eggs, with the help of its hot feet.

At the approach of the parent birds, they raise their little, palpitating bodies and open wide their tiny, orange-red mouths for food. These mouths are about the color of the meat of a peach around the stone. The veins showing through the thin skin give the bodies much the same tone. At first the young are fed by regurgitating partly digested food; later moths, caterpillars, and other insects furnish their diet. They are very fond of spruce bud moths and caterpillars. A beautiful triple spruce was attacked by these pests and almost denuded of its foliage. I noticed the kinglets frequenting this tree a great deal. In a season or two, the foliage was as luxuriant as it had been in the past. Such are the good offices performed by the golden-crowned kinglets and their young. The feet of the young are large and strong for the size of their bodies. If a person attempts to lift one from the nest, the little fellow will tear the lining out before he will release his hold. Just before the feathers appear the young begin to preen, and after that spend much of the remainder of their time in the nest smoothing and oiling their plumage. The parent birds remove all waste, depositing it far away from the little home, which is kept clean and sweet.

She continues:

I have seen kinglets feeding young in the nest as late as the last of June, but by the eighteenth or twentieth day of June, goldcrest families are usually foraging in the trees. As late as the middle of September in 1912, I saw mature kinglets industriously feeding a large family of young birds in a seedling grove.

At the time that Cordelia Stanwood was making her observations, nobody had yet discovered another amazing aspect of the kinglet’s already amazing nesting behavior. This only came to light from the loving studies, or studies for the love of the kinglet, by another pair of amateur ornithologists, Robert and Carlyn Galati who also fell for the golden-crowned kinglet. Their observations in northern Minnesota showed that kinglets not only successfully raise a family of nine to ten young in one nest, they are simultaneously busy with a second nest with as many young at the same time (Thaler 1990; Galati 1991). The phenomenon is called double-clutching.

As already mentioned, apparently the female alone builds the nest. And she alone incubates (Thaler 1990; Galati 1991). The male is the food provider. After the eggs hatch, the female has to stay on the nest to warm the naked young. The male feeds the whole family. However, soon after the young no longer need to be brooded (which is in part a function of how well-insulated a nest she had built), she deserts her young, starts to build a second nest nearby, and is then soon incubating her second set of eight to ten eggs. Her mate tends the babies of the first brood. It’s good bird parenting: despite all the hazards, nesting success is, at over 80 percent, exceptionally high for any bird (Ingold and Galati 1997).

The kinglets’ necessarily high death rate, given their high birth rate, results from living close to the energy edge in wintertime and from being weak fliers due to the heavy coat of insulating feathers they wear. Those kinglets that leave on migration suffer enormous mortality (Kania 1983; Hogstad 1984). But there are presumably similarly high losses by not migrating, or else migration would soon cease. Those that stay in winter never once stop for even two seconds in their search for food. From early dawn until dark they hop nonstop in their frenetic hunt for insects. Although they can survive nights of -40°C, severe weather and insufficient food to fuel their metabolism may produce 100 percent mortality in severe storms and icing (Lepthien and Bock 1976; Larrison and Sonnenberg 1968; Graber and Graber 1979; Sabo 1980).

The golden-crowned Kinglet is one of the three birds featured on the cover of the 1992 book Birds in Jeopardy (by Ehrlich et al.), which lists and describes the imperiled and extinct birds of the United States and Canada. However, this kinglet is not so much a rare bird as one that doesn’t attract much attention. Kinglets are difficult to see, but even then the kinglet had indeed suffered a severe decline in the early 1980s in some areas. By the end of the decade it recovered. Since kinglets have excellent nesting success and are too small to be preferred prey by most predators, the sharp dip in their population was likely due to a severe weather disturbance. Recovery can be rapid in a species with high reproductive rate, if environmental conditions improve. Kinglets in captivity have a maximum life span near ten years (Thaler 1990), but any adversity can affect them in the wild, where 87 percent of the population is on average normally weeded out every year. Kinglets are as close to an annual bird (in analogy with annual plants that regenerate each year only by seeds) as any birds gets.

For such small insect-eating birds with weak bills unsuited for prying under bark or into wood, winter is a severe enough problem that the alternative of flying thousands of miles over open ocean can be preferable. With millions succumbing annually on these dangerous journeys, there is strong selective pressure on many birds to produce the navigational sophistication and the physical and mental attributes that create and maintain the migratory capacity and behavior. At least some migrants have evolved a new sense that we lack, the ability to detect the lines of magnetic orientation of the earth. Many have evolved to be able to read the star patterns and to navigate by the constant beacon of the North Star at night. In the day they may use the sun as a compass instead. They track its movement across the sky and calculate the movement with the use of an internal time sense that is accurate to within about fifteen minutes; hence they can ascertain direction to within about four angular degrees. Physiologically, birds have evolved cycles of rapid fattening in preparation for days of unremitting flight. And most of these capacities evolved because of winter, without which none of the kinglet’s almost unfathomable capabilities would have come into existence. We don’t specifically know how golden-crowned kinglets migrate, but since they show nocturnal migratory restlessness (Thaler 1990) they therefore probably fly and navigate at night in order to be able to refuel by day.

Kinglets’ evolutionary history, and hence their biology, is linked to the Ice Ages. As recently as ten thousand years ago when the winter snows melted, there was a large, relatively uninhabited portion of the globe where insects became available in almost unlimited quantities for fifteen to twenty-four hours per day for all who would come to harvest the bounty. In the fall, when the insects became unavailable and daylight vanished, the birds retreated south. Gradually as the glaciers melted, the birds’ annual journeys to and from the rich northern feeding grounds where the days were long, became even longer. Always it was those that either could stand the cold longest or that could fly the farthest that would collect the largest bounty in the spring. They, on average, left the most offspring. Parts of the population become reproductively isolated through the glaciers of this last and previous Ice Ages. Variations, which we often arbitrarily call species, were then created. One successful group was the kinglets, which now occupy the taiga forests of the north.

Few people ever get to see a golden-crowned kinglet, even if they are looking for them (and granted, most of the population is not looking for kinglets). Golden-crowns are very difficult to see, even without the dense cover of coniferous forest in which they live. Given that sightings are difficult, the best way of determining their presence is by listening for their calls. I’m happy to report that at least at the present time, this “little king” of the forest is doing well in the dense coniferous regions of northern New England. It is rare indeed that I do not hear their pleasant Tsees in the winter woods near my cabin. The wonder is how they survive a winter night.

Whenever I return to my heated cabin on a winter day, I can be secure in the knowledge that I won’t freeze to death. Our species has a magic key for winter survival. That key, as Jack London’s story told, is fire. Other human species, like the Neanderthals, also possessed that key for probably hundreds of thousands of years. Without it, humans would not have colonized the Northern Hemisphere of the globe across Europe, Asia, and North America, all the way up to the edge of the glaciers. Fire has not only helped keep us warm and alive in the night; it also allowed us to be better predators because by cooking our meat we use it as food more efficiently. And when we were still prey, fire was also a weapon for defense.

The kinglet has occupied the same circumpolar realm that we have, and it has likely done so for incomparably longer periods of time. It has the same requirement for heat, but raised to a much sharper edge. Given its minute, twopenny weight (5 to 6 grams), how such an individual could survive the energy crunch on a cold, sixteen-hour-long winter night is an unimaginable marvel from our human perspective—it defies physics and physiology. We don’t know for sure how they do it, so we search for explanations offered by animals, and especially other birds. Their example suggests that the kinglet’s winter survival will not likely involve a new biological phenomenon or new laws of physics and physiology; I suspect, rather, it will depend on a species-specific balance created by precisely juggling a set of conflicting benefits and their costs and doing everything just right with little margin for error. There is no magic. It’s a matter of details—of getting everything just right.

I was attracted to them in part because I understood so little, and to some extent I don’t mind keeping it that way, to preserve the mystery. My pursuit of hard fact is not for the sake of facts. It’s to “capture” the story behind them.

Thaler (1990) presumed that the European goldcrest survives in winter by huddling at night to save energy, fueling itself on an energy base of springtails (Collembola), and by its ability to seek microclimates such as under cushions of powdery snow and other places. However, there is no energy balance sheet to determine the limits of these strategies, and although other birds tell us where to look, what they do does not necessarily apply to the golden-crowned kinglet which, given its North American haunts, faces even lower temperatures than its European relative. Our studies of foraging behavior of kinglets in the Maine woods (discussed in Chapter 9) showed, surprisingly, that they either did not have or did not use springtails as their main energy source. Instead, stomach contents showed that they subsisted on tiny frozen caterpillars of the moth family Geometridae. Caterpillars are not of high caloric content, as seeds are, so these little insectivorous birds would like many others drop their body temperature at night to become torpid. Nevertheless, it was presumed that reduction of body temperature at night is not necessary for winter survival in goldcrests (Reinetsen and Thaler 1988). This assessment was based on an overnight weight loss of 1.3 to 1.5 grams that was assumed to be fat. However, the birds could have a much lesser fat cushion than that, since much of the overnight weight loss could have been gut contents. Charles R. Blem and J.F. Pagels examined fat, specifically, and showed that in midwinter the extractable fat reserves accumulated by the North American golden-crowned kinglet over a day were about five times less. These authors calculated that this amount of fat (0.3 gram) would contain insufficient calories for a kinglet to maintain a high body temperature all night.

I think we vastly underestimate these, and many other birds, when we expect them to follow simple rules. Kinglets probably won’t go torpid unless they have to. As can be inferred from innumerable studies of other animals, what happens in captivity (when the animals are well fed and not stressed) may be a pale reflection of what they confront, and perform, under field conditions.

The kinglets’ main adaptations for keeping warm (and conserving energy) include those also found in most other birds. They fluff out their feathers to trap air, creating an ever-greater insulating air space around themselves. The main avenue of heat loss is then through the uninsulated bill, eyes, and the feet. During sleep, however, the first two avenues are greatly reduced as the birds tuck their heads deep into their back feathers. Reductions of body heat loss through the feet is accomplished by countercurrent heat exchange and/or reduction in blood flow, to keep leg and foot temperatures as low as possible, probably just above the freezing point of water, near 0°C. Conversely, the kinglet’s legs and feet can also be used to shunt heat from the body. For example, Thaler (1990) observed that kinglets normally have light brown legs, but when incubating their eggs, females’ legs blush to pink and red as blood is flushed through them and leg temperatures reach 39°C. (The kinglets’ broodpatch on the chest and belly is only sufficient to simultaneously incubate two to three of the up to eleven eggs of one clutch, and the heated legs are needed to constantly shuffle the eggs, and incubate them.)

In Jack London’s story “To Build a Fire,” the old-timer on Sulphur Creek had told the cheechako that “no man must travel alone in the Klondike after fifty below,” or as Alaskans quip when it is very cold “it’s a two-[or three?] dog night.” Similarly because of the danger posed by cold, golden-crowned kinglets in the Maine winter woods travel in groups of two to three or more and like goldcrests, they huddle at night. Huddling saves energy. How much heat loss an Alaskan reduces by huddling with a husky has not, to my knowledge, been accurately measured, but one goldcrest huddling with another reduces its heat loss by about 23 percent, while in trios heat loss is lowered by 37 percent, similarly to bushtits (Psaltriparus minimus), which also save the same amount of energy overnight by huddling in pairs or trios. Whatever it is that kinglets are known to do, it still doesn’t quite add up because the large energy savings achieved by huddling are insufficient to offset differences between energy reserves and energy demands. Even with huddling, hypothermia (reductions in body temperature) in kinglets is likely inevitable.

Deep torpor at night would confer large energy savings. But body temperature is unlikely to be allowed to go much lower than about 10°C, because the birds can’t risk losing the ability to shiver to keep from freezing solid if temperatures at night dip to -30° to -40°C. Survival, even with a body temperature of 5° to 10°C, would likely be impossible without the one thing I suspect matters most and that we know the least about: shelter. Migrating goldcrests stopping on a bare rocky island off Scotland, where there was no snow and little vegetation to hide in, were discovered overnighting in the open, often in groups, but many of them died overnight (Brockie 1984).

Pagels and Blem have reported seeing a golden-crowned kinglet entering a squirrel’s nest. If golden-crowned kinglets regularly overnight in squirrels’ nests, then that should indeed go a long way toward solving their problem. In magnitude, it would be the equivalent of them inventing fire, because it would conserve body heat by enormously reducing convective heat loss. However, squirrels are notorious predators of (young) birds who can’t fly, and red squirrels even prey on young snowshoe hares. A tiny kinglet would be a tasty snack for a squirrel. How would a kinglet know if a squirrel nest is uninhabited and worth the risk of entering?

In the winter of 2000-2001, I hunted for and examined dozens of both red and flying squirrel nests in the Maine woods. I became skeptical that these very snug nests (see Chapter 5) could be or were used by kinglets that were active in the same coniferous woods. First, although each nest had two entrances, these entrances were difficult to find. To introduce my hand into a squirrel’s nest I had to force it through thick dense nest material; it felt like forcing one’s hand through an elastic glove opening that normally stays shut. Could a bird squeeze through? I found no bird feces inside any nest. In all the snow caves where ruffed grouse had overnighted, I found dozens of fecal pellets, and I presume that kinglets entering squirrel nests with a full stomach at night would also have had to void their bowels in the night. I therefore asked Blem for more details. He e-mailed me: “My single observation of kinglets and squirrel nests was very brief, but I definitely thought the bird disappeared in the nest. I could not say that it went into a main entrance. It seemed that it just went into the loose leaves on the outside of the structure.”

Since reading about Pagels and Blem’s interesting and provocative observation I have been stimulated to stay alert and try to find out where kinglets spend their winter nights, because all indications are that the overnighting roosts are crucial to their survival. I’ve followed them at dusk, again and again, but always lost track of them as they continued to forage and eventually faded and vanished into the darkening foliage of conifers, usually with no squirrel nest in sight.

In early January 1995, I thought I was finally getting close to tracking them to a sleeping place. I had noticed a group of three of them in the spruces near my cabin, and on January 5 I saw them again and followed them for eighty minutes. Finally, as it was getting dark, I heard them make some persistent soft tsees, then many louder ones, and then, at 4:20 P.M., the birds suddenly became quiet and vanished from sight. But it was just getting too dark to see. The next evening I waited near the same area till 4:30 P.M., and saw nothing. A student, Jeremy Cohen, took over near the same site the next three evenings, and he managed to follow a (or the) group of three kinglets on one evening, again until 4:30 P.M. when it was almost dark. None had entered the three local red squirrel nests that I had located near there previously. At dawn the following day, I arrived with Cohen and other trackers at the same site where they had been last seen on the evening before, and we did indeed see three birds just as it was getting light. But it was not near a squirrel nest. I then became ever more doubtful that the kinglets’ key to winter survival in the Maine woods could be traced to squirrel nests.

I also doubted that kinglets would routinely burrow into the snow on the ground and dig tunnels like grouse do. That is because I’ve frequently encountered rainstorms followed by icing that produced thick crust on the snow. Only a large strong bird can escape the icy prison, or last it out till the ice melts. It seemed possible, however, that kinglets could burrow into the undersides of snow cushions on branches, and in that case they could again escape from below, because the ice crust forms only on top.

In the winter of 2000-2001, I and my Winter Ecology students again made it one of our projects to try to pursue kinglets to their sleeping quarters. Again we were unsuccessful in tracing any birds into a squirrel nest. Nevertheless, we probably got closer than ever before to what they actually do. It was by accident.

Two kinglets fluffed out and huddling in a snow cave on a branch.

On December 19, one of the students, Willard Morgan, went out before sunrise to enter a hiding shelter we had built out of brush to watch ravens (where they could not watch him) arriving at a carcass. On his way to that shelter, while walking in the semidarkness, he flushed two kinglets almost off the ground at his feet from under a brush pile he passed. The brush was covered with cushions of freshly fallen snow. The previous night had been windy and blustery, with sleet and snow. Being close to the ground and tucked under the snow cushions in the brush pile, the kinglets would have escaped the weather. Morgan returned to the same site to watch in the next two evenings, but the kinglets did not return. This observation strengthens my suspicion that kinglets, in order to forage to the last minute of the day, are forced to use any of a variety of shelters, not only that in or under a squirrel nest. If so, their behavior places ever more burden on both deep nocturnal torpor and simultaneously the necessity of shivering all the night long.

The cheechako, in Jack London’s story “To Build a Fire,” died in the Alaskan winter not because he made one big mistake. He was just unlucky and also made tiny errors that accumulated and amplified, until they made all the difference. I conclude that the kinglet similarly, but oppositely, has no magic key for survival in the cold winter world of snow and ice. Those that live there are lucky and do every little thing just right. The odds of surviving the winter are slim, but the gamble, as in the breaking of the buds and the winter hive exits of the bees, has risks that must be taken. The unlucky rolls of the dice that result in individual deaths are absorbed by a high reproductive rate.

Lucky for a kinglet, it does not know the odds stacked against its individual survival. Presumably it could not contemplate its fate, regret about mistakes, or fret over injustice or lost opportunities. It does not worry about the future, or about life and death. Why can we presume this? Because these mental capacities could only compromise, not aid survival. They could not activate the bird to effective action, because there is so little, if anything, it could do to change things in its world where the relevant things—ice storms, a subzero night, winds, food scarcity—are ruled by chance. Undampened enthusiasm and raw drive would matter. I do not and cannot ever know the combination of happiness, hunger, or emotions that energize a bird. But whenever I’ve watched kinglets in their nonstop hopping, hovering, and searching, seen their intimate expressions, and heard their constant chatter of tsees, songs, and various calls, I’ve felt an infectious hyperenthusiasm flow from them, and sensed a grand, boundless zest for life. They could not survive without that in their harsh world. Like us, they are programmed for optimism.

I am gladdened to know that a population of these wraiths of the forest thrives. When I’m in the warmth of my cabin and hear gusts of wind outside that moan through the woods and shake the cabin on wintry nights, I will continue to marvel at and wonder how the little featherpuffs are faring. They defy the odds and the laws of physics, and prove that the fabulous is possible.