For some, the decreasing hours of sunlight are an invitation to a long winter's nap.

To Pennsylvania's Great Horn Owl, it's a hoot.

This original night owl doesn't become active until sunset, and in winter, from 10 p.m. to 2 a.m., it's party time since the hooters are a'courting.

"What we are noticing now is an increased vocalization in the birds," said Franklin Klock, a naturalist at the Carbon County Environmental Education Center. "They are largely nocturnal, so we hear these sounds at night. The Great Horned Owl is the classic hoot owl that people hear.

"You may hear conversations through the woods with these owls, back and forth ... constant hooting," he continued. "It may be males claiming a territory, or females calling a male into their territory, but usually it is the males that are working to attract the females."

Night owls who follow the great horned owl, will hear their deep "whoo-whoo-whoo" call. On bright moonlight nights the hooting of the horned owls becomes noticeable about a month before the actual mating begins. When they are courting, there is a slight difference in the tone of the hoots.

The smaller male has the deeper voice, and hoots more frequently. In search of a female, the male may hoot for four to six weeks while an interested female may only hoot for one or two weeks towards the end of the male hooting period.

"The interesting thing about great horned owls are how they receive sound," Klock noted. "The circles around their eyes are what they use to receive sounds."

He explained that the dished shape of their eye sockets capture sound similar to a satellite dish. Between the low frequency hoots and their dished receptors, great honed owls can locate a potential mate several miles away.

As they near the time of selection of a mate, you can hear the hoots of several birds calling back and forth steadily. At times, the hooting may last nearly all night.

"Once the male and the female meet, to entice a female, the males do kind of a dance, walking around bobbing their heads up and down," Klock said. "It also involves some beak rubbing that the male and female will do before breeding."

The great horned owl doesn't build a nest, it locates one that has been abandoned by another bird. Around the end of February, about a month after breeding, the female begins laying eggs in the nest.

"They are asynchronous layers and hatchers," Klock noted. "The female lays two to five eggs, usually days apart."

If there is not enough food, the youngest become food for the oldest.

The newborn are protected by their mother's warmth during those first vulnerable days of life during the frigid February weather. They quickly grow a layer of insulating down. Unlike most birds, the feathers that they will soon grow will cover them all the way to their talons.

After about six weeks, the fledglings are too big for the nest and begin wondering the tree limbs and the ground. Although unable to fly until about ten weeks, they begin using their talons to feed themselves, while their parents keep watch to feed them as a back-up.

The great horned owl is one of the most powerful hunters of all birds. Its combination of excellent nighttime vision, three-dimensional dish-aided hearing, silent flight, and deadly talons make it a perfect predator. While most of its diet is composed of mice and rats, it has been known to kill rabbits, snakes, woodchucks, chickens and turkeys. Because it lacks a sense of smell, it is one of the rare predators that attacks skunks. Like other raptors, they swallow their food whole, regurgitating the indigestible parts.

The great horned owl is the most populous owl species in the United States and the largest species of owl in Pennsylvania.

"It's not uncommon to reach 13 to 16 inches tall," Klock said. "It will only weigh about two and a half pounds, but can carry up to half its body weight. A large female could have a wing span of almost four feet. Females can be up to a third larger than males. Great horned owl live to 26 years in captivity and about half that in the wild."