Woodcock habitats are diminishing, squeezed from opposite ends. Human development is one major cause, but nature’s development is another: In places where young forest matures, taller trees lead to a more open understory by starving the low brush that woodcocks prefer. Woodcock numbers have declined an average of 1 percent per year since Geis and Rouse watched this ritual 50 years ago. In Maryland, their decline has been even steeper, averaging 4 percent per year. Across their range, which includes the eastern half of the United States and southern Canada, there were well over a million more woodcocks 50 years ago than today. Scientists at the North American Bird Conservation Initiative have placed the American Woodcock on their Watch List of species needing proactive conservation measures. More than 60 other species also need young forest habitat, including warblers, towhees, catbirds, rare cottontail rabbits, and endangered wood turtles.
But here, at least, in this parkland clearing, woodcocks still flourish, nestled under the thin spindly trees standing upright two stories tall all around us. Detweiler identified the trees as tulip poplar. “The buds look like duck bills,” he said. Finally, Cummings called everyone to listen.
We waited, then heard an up-pitched chirp, which Cummings whispered was an Eastern Towhee’s call. Noticeably darker, a red remnant of the sun’s presence dimmed above the tree line. A reclining crescent moon appeared between the clouds in the southwestern sky. Peent.
There it was! Peent. A nasally buzzer sounded off to the west. Peent. The time was 6:24 p.m., 12 minutes after official sunset. Peent. The peents sound every three seconds.
Analyzing unique bird calls has provided insights. Before sunset, Cummings showed us spectrograms of peent calls he had recorded in the past. The first graph, relating sound frequency with time, showed the sound’s strength by light and dark shading. The page displayed a pattern of vertical ribs, resembling a bad print job. But the ribs depicted sound that went on-off-on-off in quick succession over the course of each 0.2-second peent.
The peents come from vibrating muscles in the woodcock’s throat. Their on-off pattern parallels an analog electric buzzer, according to Cummings, where a charged electromagnetic coil attracts an adjacent metal plate. But when the plate moves toward the coil, it breaks the circuit, turning off the magnetic field, which causes the plate to fall down again and turn back on the circuit. This process keeps repeating — on, off, on off, with the metal plate buzzing as it moves back and forth between the coil and circuit contact many times per second. “That’s the way an electric buzzer works, and these birds sound a lot like it,” Cummings explains.
Peent. We walked slowly to the western edge of the clearing. The calls were coming from the grass trail beyond. In the dusk, we could just make out a dark shape on the turf. The woodcock was shuffling its feet.
Another of Cummings’ graphs illustrated the shuffling with sound waves. Plotting the sound’s strength across time, each peent was clearly visible with a sharp, rounded spike. But a second pattern also emerged: Connecting the peaks of each peent wave formed another, gentle wave. Cummings explained that the bird shuffles to change direction after each peent to broadcast his presence to as many surrounding females as possible, eventually making a circle. The highest-peaked peents come when the bird faces the sound recorder, and the lowest when he faces opposite. Nine peent spikes could be counted between the highest peaks, so that meant the woodcock shuffled about 40 degrees after each peent.