by Ella Sorensen
Six feet above the cattails the Northern Harrier quarters, then flies tilting back and forth, side to side, flashing a rump patch of brilliant white. The curved bill points downward while two yellow eyes in a face fringed with a ruff of feathers scans below.
Intent, focused, listening.
With a banking motion, the harrier catches the wind for a long gliding sail along the border between cattails and open water, flaps a few flaps, and glides again.
Back to the cattails it goes, suddenly halts - almost somersaults backwards, fans its banded tail widely, flaps its wings to hover stationary for a moment and drops, disappearing into the vegetation, to emerge shortly flying away with a furry ball clamped in yellow talons; a long tail daggling down.
Hunting success! Studies give successful prey capture at 5-35%.
Harriers are birds of the sky, occasionally flying high or even soaring. Their courting sky-dance of acrobatic U-shaped loops and head over wing stalls is legendary. Mostly though, harriers are found, not high, but flying low, in close and intimate proximity to the earth. It appears as if they fly through empty space, flapping and gliding, tipping and tilting their v-held wings. But harrier flight, executed so buoyantly graceful with such apparent ease, is in reality a complex interplay between feathers and weight with the invisible molecules of air that they adeptly harness to maneuver their flight. Harriers forage on the wing when the air is calm and still. They also capture the powers of the wind, for when gentle and moderate breezes come calling, harrier velocity and acceleration increases as they ply the air currents, adding strength to their movement. Strong winds become too erratic of a partner to trust and harrier activity decreases.
Harriers are on-the-wing predators, covering sometimes a hundred miles a day. Voles are a primary food source around Great Salt Lake, but harriers are opportunistic in their hunting and take a variety of mice, rats, frogs, snakes, insects, and songbirds.
Harriers hunt primarily by sound. The ruff of feathers that gives the face an owl-like appearance is a sound gathering mechanism.
William Rice of Oregon State University tested the ability to locate prey by sound of the harrier, two owls: barn owl and short-eared owl, and two diurnal raptors: kestrel and red-tailed hawk. The harrier’s ability to determine the horizontal direction of sound greatly exceeded the two hawks. The harrier’s ability to determine that direction was indistinguishable from the two species of owl, both which have the ability to locate prey in total darkness.
Harriers have hunting options but unlike owls, they shun the darkness. As the sun sets and twilight dwindles, harriers drop down to roost. At first light, after resting the night, harriers rise once again to begin their day of foraging.