Anyone who spends time outdoors at this season is likely to notice that many wild creatures have begun to synchronize their movements and activities. Perhaps the most commonly observed example of this phenomenon is the flocking of birds, such as blackbirds, as they prepare for fall migration. But the behavior is by no means limited to birds, and is widespread throughout the natural world, especially among the insects.
Sometimes the appearance of many individuals of a species in one location may be explained by the availability of a food source. Recently I was enthralled by the sight of dozens of American lady (or American painted lady) butterflies feeding on the nectar of goldenrod flowers. The more I looked, the more butterflies I saw, opening their colorful orange-and-white mottled wings in the bright afternoon sunlight, like so many stained glass panels, and closing them to reveal the two large “eyespots” on their hind wings that distinguish them from the closely related painted lady butterfly.
Both the American lady and the painted lady are migratory butterflies, like the more famous monarch, but their migratory habits are less well understood. It’s not known, for instance, whether these predominantly southern butterflies can survive northern winters as adults, or whether they rely on northward migration in the spring to repopulate the northern parts of their range each year. Perhaps the flock of American ladies I came upon last week in Portland, Maine was headed south towards our region, and had simply paused on their journey to feast on the abundance of goldenrod in bloom among the sand dunes.
The importance of goldenrod in sustaining the southward migration of monarch butterflies cannot be doubted. We just released a newly emerged monarch butterfly we had watched as a caterpillar as it chewed its way out of its tiny white egg, fed upon the milkweed leaves we supplied it, formed a chrysalis, and has no doubt by now joined other adults of its kind on the long trek towards Mexico. We wished it luck and safe travels as we watched it spiral upward in its flight above our home.
Perhaps the largest and most conspicuous of our dragonflies, the green darner, is likewise a long distance migrant. Green darners can often be spotted now in groups of a dozen or more, flying through the swarms of midges or gnats that rise and fall in unison in the warm late summer air. As they pass through these insect clouds, their clear wings shimmering in the sunlight, jaws open and legs bunched up to form a kind of scoop net, these insect hawks are fattening themselves for their journey, which will follow landforms like our Shawangunk Ridge, and the coastline. In doing so, they will share the skies of September with migrating birds of prey.
Though it’s not known exactly where they are headed, green darners are likely to fly, in aerial dragonfly rivers, at least as far as the Gulf of Mexico, and perhaps, like the broad-winged hawks, all the way to Central America.
Synchronized behavior in the animal kingdom can be heard as well as seen, and occurs in creatures who never stray far from their place of birth as well as in migratory species. We are all familiar with the spring chorus of spring peepers, for example. The chanting in unison of cicadas by day and katydids by night has been described in an earlier column.
A fellow New Paltz resident has reported recently hearing a chorus of crickets whose singing was synchronized in this way, “creating an unearthly metallic aural sheen.” My guess is that he was hearing a performance of snowy tree crickets. These delicate, ghostly pale insects are known for the regular pulse of their chirping. In fact, they are sometimes called the “temperature cricket” because their chirps increase in frequency as the air gets warmer, in such regular fashion that one can tell the temperature in degrees Fahrenheit by counting the number of chirps in thirteen seconds and adding forty.
Certainly the swarming of insects and flocking of birds has a certain survival value for these animals. There is safety in numbers for prey species, who may confuse and thus elude would be predators by traveling in large groups. Beyond this explanation, and the tendency for many individuals to congregate at a common food source, there are more questions than answers when it comes to synchronicity among many animals. Whether we are listening to a chorus of crickets, or gazing at the swirling dance of starlings that wheel as one body in the air, we are confronted by an essential mystery of creation, to which the natural human response is awe.
Richard Parisio is a lifelong naturalist, educator and writer. He currently leads field trips for school classes at Mohonk Preserve, teaches courses about John Burroughs and conducts tours of Slabsides and the John Burroughs Sanctuary for groups and individuals by request. Rich is New York State coordinator for River of Words, a national poetry and art program on the theme of watersheds, and teaches River of Words programs for school classes, grades K-12, by request. Contact Rich (firstname.lastname@example.org) with questions, comments, or suggestions for Nature at Your Doorstep.