Wood ducks and the flooded nest box
June 5, 2026
The nest box tilts slightly over dark water near Clarksville, its entrance hole facing the cattail marsh. Inside, a wood duck hen sits on eleven cream-colored eggs, her iridescent green head catching fragments of light that filter through the wooden walls. The box was mounted here in early spring when the water was lower, but June rains have raised the pond level until the structure appears to float above the shallows.Wood ducks are cavity nesters by necessity. Unlike mallards or geese that build ground nests in tall grass, wood ducks seek the protection of tree hollows or nest boxes elevated above predators and flood waters. The hen selected this box in May, inspecting the interior with her bill before laying her first egg. She has been incubating for three weeks now, leaving only briefly each morning to feed on duckweed and aquatic insects in the surrounding marsh. Her drake departed after mating, molting somewhere deeper in the wetland complex where he will remain flightless through midsummer.The timing of wood duck nesting aligns precisely with the peak emergence of aquatic insects and the longest days of the year. Ducklings that hatch in early summer will have maximum daylight hours for foraging and the richest invertebrate populations to sustain their rapid growth. Mayflies, caddisflies, and midges pulse from the water in waves throughout June and July, providing the protein-rich diet that young wood ducks require. The hen times her nesting so that her brood will hatch just as these insects reach peak abundance. A clutch that hatches too early faces cold nights and sparse insect life; too late, and the ducklings must compete with juvenile waterfowl from earlier broods for diminishing food resources.The flooded condition of the nest box creates both opportunity and risk. Higher water levels bring the box closer to prime feeding habitat, shortening the distance ducklings must travel on their first day of life. When they hatch, the young will tumble from the entrance hole into the water below, using their natal down as flotation while they learn to dive for insects and small crustaceans. The deeper water also provides escape routes from terrestrial predators and access to submerged vegetation that supports the invertebrates they need. But flooding can also trap adult birds inside boxes with entrance holes too close to the waterline, and sudden water level changes can strand developing eggs if the hen abandons a compromised nest.Listen for the soft murmuring calls that drift from the box in the early morning hours. The hen talks quietly to her developing brood, a low conversational sound that will help the ducklings recognize her voice when they hatch. In another week, if the water holds steady and the weather remains warm, eleven small heads will appear at the entrance hole, ready to leap into the world below.
Brown-headed Cowbirds and their unwilling hosts
May 21, 2026
The air carries the sound of unseen drama in the canopy above Clarksville. Somewhere in these leafed branches, brown-headed cowbirds are searching. The female moves through the territory with purpose, her dark eye scanning for the flash of movement that betrays a nest under construction. She has no nest of her own to build, no young to feed directly. Instead, she practices an ancient deception that turns other birds into unwilling foster parents.The cowbird follows a careful schedule. She watches. She waits. When a yellow-throated vireo begins weaving its pendant nest in the fork of a white ash, or when a prothonotary warbler claims a cavity in a dead snag, the cowbird takes note. These are her targets. She memorizes their locations, their routines, the precise timing of their egg-laying. Then, in the brief window before dawn, she strikes. The host birds leave their nest for minutes to forage. The cowbird slips in, removes one of their eggs, and deposits her own in its place. The entire transaction takes less than sixty seconds.What happens next reveals the evolutionary pressure this relationship creates. The cowbird egg hatches earlier than its nestmates. The cowbird chick grows faster, begs louder, and often outcompetes the host's own young for food. The yellow-throated vireo parents, responding to the largest, most demanding mouth in their nest, may inadvertently starve their own offspring while feeding the imposter. Some prothonotary warblers have developed defenses. They recognize the cowbird egg and abandon the nest entirely, starting over elsewhere. Others build a new nest floor directly over the cowbird egg, burying it beneath their own clutch. But many simply accept the substitution, their parental instincts hijacked by a chick that will never learn their songs or migration routes.The cowbird's strategy works because it exploits something fundamental about parental care in birds. The impulse to feed a gaping mouth is stronger than the ability to recognize one's own young. This creates a strange economy in the forest canopy. The cowbird population can grow without the constraints that limit other species. They need no territory for nesting, no energy spent on nest construction or chick care. Meanwhile, their hosts bear the hidden cost. Each successful cowbird reduces the reproductive success of species already facing pressure from habitat loss and climate change. Listen for the cowbird's liquid notes filtering through the leaves above. Somewhere nearby, this ancient transaction continues, as quiet and relentless as the morning light moving through the branches.
