As songbirds were settling into their nighttime roosts, a flock of humans wearing long- sleeved shirts, long pants, sneakers, and glazed in insect repellent set off afoot in search of night shift creatures at Congaree National Park.

On Friday nights for three months each spring, fall park rangers lead strangers along a 2.5 mile boardwalk from the Visitor Center to Weston Lake. The Owl Prowl has been a popular program for over 20 years, and its right in our backyard.

Fireflies provide natural circular puffs of light along the way. Adults and children carry flashlights covered in red cellophane to help their eyes adjust to the dark and to assist in uncovering mysterious phenomena.

Scanning the flashlight into the swamp beneath the boardwalk can detect snakes and skinks. Swinging the flashlight overhead deciphers bats. The ranger instructs on how to angle the flashlight on the forehead or nose to find glittery eyes of spiders along the forest floor. Finding spider eyes is a difficult task in daylight, but it is actually easy and cool at night.

Park ranger Corrine Fenner uses a feather and foot to teach how owls hunt prey silently. As observers walk in silence, the owls begin to communicate. Three species of owl make their home in the Park: the barred, the eastern screech, and the great- horned. Of the trio, the barred prefers the flood plain environment the most.

Barred owls are territorial and monogamous. They nest in woodpecker holes and raise one brood per year. Their loud "hoo, hoo, hoo, hoo" sometimes interpreted as "Who cooks for you?" is heard repeatedly during the two hour hike, sometimes coming from the distance and at times right overhead. Owls are more likely to be heard than seen on a prowl.

Owls are master predators by design. Their large eyes face forward giving them strong binocular vision. The eyes are not balls but elongated tubes held in the socket by bony sclerotic rings so they cannot move independent of the head. However, the owl can swivel its neck 270º to compensate. The retina of an owl eye is filled with rods rather than cones making it sensitive to black and white light and movement in the dark as well as day.

An owl's facial disc focuses sound like a satellite dish. Ear openings are asymmetrical. Usually the right ear is lower than the left. An owl adjusts its head up or down to equalize the source of the sound in both ears and look directly at the source. Ears are very sensitive to high pitched sounds like squeaking of rodents or rustling of reptiles and amphibians.

Owls are silent predators. In the shelter of a 250- year old loblolly pine, the ranger displayed the wing of a great- horned owl pointing to the fringed edges of the primary flight feathers which dampen sound. Then she took an owl foot from her backpack. The feathered talons silence the hunt too. Each foot has four toes with razor sharp talons that instantly pierce prey and puncture vital organs.

Talons are made of a bonelike structure called keratin. After an owl captures prey with its feet, it uses its strong hooked beak to crush the head. Small mammals, birds, fish, reptiles, amphibians, and arthropods are on their menu.

Owls swallow prey head first. Since much of what is consumed is indigestible, they regurgitate compact wads of bones, fur, feathers, and exoskeletons as pellets. Often pellets are the first sign of owls in a garden or neighborhood.

Scientists have studied pellets to find out the preferred diet of various species. We know owls are beneficial in controlling rodent populations.

Stopping to listen to more music of the night from frogs at Weston Lake, phosphorescent insects fly among the trees. Sometimes glow worms and flying squirrels entertain.

Owl Prowls resume at Congaree National Park again in the Fall.

www.nps.gov/ cong