Night herons hunt the summer emergence

The sun sets late over the waterways near The Heights, leaving a long dusk that stretches into the blue hours of early summer. This is when the Black-crowned Night Heron begins to move. From the shadows of the sycamores and maples along the water's edge, these stocky, pale gray birds emerge to take their positions in the shallows. Their thick necks are drawn close to their bodies, and their bright red eyes scan the surface for the slightest movement.

Early summer brings a surge of life from beneath the water. Mayfly nymphs, dragonfly larvae, midge pupae, and caddisfly cases that have spent months or even years developing in the mud and vegetation of ponds and slow-moving streams are now ready to transform. They rise toward the surface in waves, breaking through the water tension to shed their aquatic skins and emerge as flying adults. This emergence happens most intensely at dusk and into the night, when predatory fish are less likely to see them and when cooler air temperatures help preserve their delicate wings. The timing could not be better for the night herons, who are most active in these same twilight hours.

The Black-crowned Night Heron is built for this kind of hunting. Its eyes are positioned to look forward and down, giving it binocular vision to judge distances accurately in low light. When an emerging insect breaks the surface or a larva moves through the shallow water, the heron strikes with startling speed. Its neck, compressed like a spring, shoots forward and the sharp bill pierces the water with barely a splash. The bird swallows its prey immediately and returns to its motionless stance. This is not the patient, slow-motion hunting of a Great Blue Heron in daylight. This is quick, precise work that takes advantage of a brief window of abundance. The aquatic insects are most vulnerable during their emergence, when they must reach the surface, split open their larval cases, and pump fluid into their new wings before they can fly. Those few minutes of transformation are when the night herons feed most successfully.

The relationship extends beyond individual hunting success. These nocturnal herons help regulate aquatic insect populations at a critical life stage, and their feeding concentrates nutrients from the water back onto land through their droppings. The insects themselves are completing an ancient cycle, moving energy and minerals from the aquatic environment where they developed into the terrestrial world where they will mate and lay eggs. As the last light fades from the western sky and the first stars appear above the city, listen for the harsh calls of the night herons as they establish their hunting territories. The water around you holds this same emergence, this same patient hunt, this same movement of life between worlds.