The bat and bug flights at dusk
The last rays from sol are disappearing behind the forests to the west. The red and gold glow given by these trees now has the sunset spectrum on the horizon, forming a backdrop. Sunset is earlier each evening now, but on a clear day like this light lingers for a half hour or more. The temperature of about 50 degrees and calm winds help bring this marvelous autumn day to a close.
The day was one of sunlight, "October's bright blue weather" in mild temperatures. Migrant sparrows, warblers and robins were in the yard. And I noted a sapsucker and flicker passing through as well. Geese and crows added plenty of sound to the south-bound birds. Taking advantage of the ripe acorns (and sunflower seeds from the bird feeder), our resident chipmunks spent this fall day putting away provisions for the coming cold. And the forest was filled with yellows and reds, appearing almost as though every tree had been painted.
All this diurnal activity is now slowing as night is moving in. I am out for a walk to a nearby swamp to watch a performance at dusk. A flock of juncos call and move further back from the road as I pass by. In the nearby woods, I hear the call of a hermit thrush and a ruffed grouse drums. Far off in the east, a great horned owl is welcoming the coming darkness with a series of hoots. As I approach the swamp, I'm greeted by a snipe flying over and a couple of wood ducks leave to go to another secluded site. A muskrat paddles just off shore as it dives and dines on aquatic roots. The swamp is always full of activity and this evening is no different. But I'm here to watch the maneuvers of bats that fly and feed overhead. Dusk is the time of the flight of the big brown bats.
All of the seven species of bats in the Northland feed on insects. They have been with us since spring and catching and devouring insects each day. Now most have prepared for winter by moving south; like birds, they migrate. These big brown bats will soon be dispersing as more chill moves in. They spend the dark, cold times either further south or in a shelter, maybe our buildings. But the bats that I came here to see are sticking around later than most and are still finding insects at selected sites. I have seen these bats active as late as early November.
I have been watching bats at this swamp each evening for several weeks. They arrive about 10-15 minutes after sunset and in the waning light and I'm able to observe them clearly. They gather, anywhere from a pair to a half-dozen, to fly over this wetland. Water cools slower than the surrounding land and so insects remain active here. Above the water, in the diminishing light, I see the movement of autumn crane flies. These insects, often confused for mosquitoes, are competing in a flight to determine mate selections. They are oblivious of both the bats and me. Many get snatched as do some late-season moths. But it is the flight of another insect that gets the attention of all of us: the giant water bug.
At 2 1/2 inches long and having a robust body, these insects are one of the biggest in the region. Besides the size, they are equipped with powerful pincher-like front legs and a pointed, puncturing mouth. All through the warm season, they lived in this shallow water world feeding on whatever was available: other insects, tadpoles and even fishes. Now as the days shorten and the temperatures drop, they take flight at dusk. It appears that these powerful insects will leave such a shallow scene to head for a larger, deeper aquatic site for winter. The flight is one of danger and the predators may quickly become the prey.
As I watch the bats maneuver this space above the swamp, I see how they turn, twist and dive in response to insect-catching strikes that I cannot see or hear. But when a giant water bug arrives, most bats will find it. The 4-inch bat handling a bug more than half its size in midair is quite an accomplishment and a full meal. If the giant water bugs pass the bat zone, they proceed to a lake. We usually do not see this part of the journey, but sometimes they get confused by the presence of our lights. Here they will fly into exhaustion and collapse to the pavement. We might find them the next day. This explains their other name of electric light bug.
I watch this dramatic show until it's too dark. A barred owl calls as I walk back to the house and off in the distance, coyotes are yipping. I pass sprinkles of light along the roadside soil as several glow worms (firefly larvae) move about. I was able to witness a great flight at dusk and the beginning of a fall night.
Retired teacher Larry Weber is the author of several books, including “Butterflies of the North Woods,” “Spiders of the North Woods” and “Webwood.” Contact him c/o firstname.lastname@example.org.