Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [123]
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