Wild Side : Slow down, sop up the season
One of the Islands' most predictable human events, the post-fireworks, post-fair exodus, has brought relief to drivers negotiating Five Corners. Tourism winds down as seasonal residents and workers leave to resume their real lives. And corresponding to these external changes, the internal landscape of a Vineyarder changes, too. You encounter fewer faces in the course of a day, and feel happy to recognize a higher percentage of them. As the roads grow less jammed, it feels more natural to wave someone to go ahead of you. It no longer seems quite as important to beat the lady with the overloaded cart into the checkout line in Cronig's.
The Wild Side does not do sociology, but it's clear that the end of "the season" alters the internal as well as the external landscape for human Islanders. It should come as no surprise, then, that similar changes take place as August winds down among the non-human wildlife of the Vineyard. But as with the changes in human society, there's more to it than the departure of migrants. Plants and animals behave differently and experience profound physiological changes as summer ends; even as summer lingers, the natural world is preparing for winter.
One obvious change is the decline in bird song. Early migrants like yellow warblers and orchard orioles are gone entirely by now, or are temporarily replaced by non-singing migrants from farther north. But even among the residents that will overwinter, singing has practically ceased by Labor Day. With winter approaching, there is no sense in starting another crop of youngsters. And with no need to breed, there is no need to attract a mate or defend a territory. Pugnacious through most of the summer, birds grow mellow and gregarious as August ends
For some species, though, it isn't just a decline in the urge to sing that brings on silence. It can be the actual loss of the ability to sing. Song sparrows, for example, are among our noisiest musicians through the summer; a male may spend the majority of each summer day singing from a perch, claiming exclusive territory and trying to sell his genes to females. During August, this activity tails off as hormonal changes both cancel the mating urge and reduce the size of the bird's vocal apparatus. By mid-fall, the best this impressive singer can manage is a gurgling remnant of its springtime song. By November, the species stops singing altogether, not to resume until late winter.
Among insects, too, the summer cycle comes to a close. Leonard's skipper, the species with the latest flight period of our resident butterflies, appears around the first of September. The adults, brick-red and less than an inch long, spend September nectaring on goldenrod and chasing each other in courtship or territorial flights. Their eggs will hatch, their caterpillars will mature, and their chrysalids will go dormant beneath the leaf litter, all by the middle of October. Once this species is on the wing, an observer knows the season is ending. Butterfly diversity decreases steadily from here, until the last, hardy individuals peter out in early December.
But there's more to it than that. Unlike Leonard's skipper, many of our butterflies go through multiple generations in the course of a year. American coppers, for example, are on the wing in May; the descendants of those individuals appear in July; a next generation completes its development in September. And then, miraculously, the process stops. Adult coppers would freeze to death during winter. But copper eggs laid in September or October simply don't develop, lying dormant instead on the ground until prompted to hatch in early spring, with the resulting caterpillars maturing rapidly to produce next year's first flight. In one way or another, all our resident butterflies accomplish something similar, arresting their life cycle at a stage that has evolved specifically to survive the winter.
What drives these profound changes among wildlife? While the weather may exert some effect, it would be risky for a species to rely on weather alone for its cues. A warm September could produce risky hormonal changes, launching a breeding cycle when the species would be better off preparing for winter. A much more reliable trigger for behavioral and physiological change is day length: daylight has been shortening since the solstice back in June, and the rate at which this change occurs increases to a maximum at the time of the fall equinox in September. Laboratory experiments have shown that by manipulating length of daylight, one can control hormones, behavior, and dormancy in many species.
I don't think humans are immune to the effects of shorter days. Why should we be? We're animals as much as the sparrow and the butterfly. So relax and enjoy the process of slowing down, as the seasons wind toward winter.
