Sigworth said she called her next-door neighbor, who also spotted "something walking around." She then called law enforcement.
She said two Harford County sheriff's deputies responded and searched the yard. Sigworth said one deputy found tracks and called her over to look at them.
She said the deputy told her the tracks were not human but were bear tracks.
"I thought the guy was kidding when he said it," she said of the deputy. "This is a neighborhood."
Edward Hopkins, spokesman for the Sheriff's Office, confirmed the deputies went to the Sigworth home on Jan. 29 regarding a "prowler call," but they did not write a report or take pictures of the tracks.
The Rochelle Meadows neighborhood where Sigworth and her family live is off Route 152, not far from Fallston High School. The Fallston Recreation Complex is slightly more than one mile to the northwest.
The neighborhood is also within two miles of the sprawling Gunpowder Falls State Park that straddles the Harford and Baltimore county line. The park has hundreds of acres of woodlands and rock outcroppings in the Fallston area alone.
Sigworth said there is a wooded buffer, which she estimated is about 10 feet wide, between Rochelle Drive and the houses to the northwest of her.
"I'm kind of happy it wasn't a person standing there, but a bear is just as bad, I guess," she said.
Sigworth's brother, Bobby Kerner, was house-sitting about a month later when she and her husband were out of town.
Harford County does not have a resident population of black bears – they are typically found in western Maryland — but bears have been known to wander across the entire state and to visit Harford in their travels.
"The Susquehanna River is a great travel corridor for all species of wildlife, including bears," Harry Spiker, the state Department of Natural Resources bear biologist, said Thursday.
Spiker said mother bears typically hibernate with their young during the winter, "but it is possible; we have had reports of them up and moving throughout the winter."
He noted young bears begin moving through the state during the spring and summer "dispersal" system, when their mothers force them out of the den.
Bears were sighted at least three times over about two weeks in June 2012 around Darlington, Webster Village and Susquehanna State Park near Havre de Grace.
The bears – probably two different animals based on accounts from people who encountered them – were seen near homes during the day, and several people snapped clear pictures of the creatures wandering around their yards.
Spiker stressed bears typically try to avoid people, explaining they are wandering until they find other bears for mating purposes.
They can, however, become nuisances when human beings try to feed them, he said.
Spiker recommended people secure their trash cans and bird feeders, both of which can attract bears.
Sigworth said she reported the bear sighting to The Aegis because she was concerned for the safety of neighborhood children and pets.
"With warm weather coming I just want people to be aware of it, because I'm sure all their kids will be outside playing," she said.
Kerner, who lives in Edgewood and has been Harford County resident since 1985, said he had never seen a bear in the county before last week's encounter at his sister's home in Fallston.
He also never saw one while growing up in Parkville and camping out with his friends in Harford County.
"We camped out, and they had a little cabin up on Ady Road, and I was up there all the time, and I have never, ever seen a wild bear," he recalled.
Kerner was also concerned about the risk to children and pets, but Spiker again stressed bears typically try to avoid humans.
The biologist said people who encounter bears should not try to stare them down or chase them, but rather they should back away and make noise to get them to leave.