Hamilton's peregrine falcon project is back to square one after the city's resident falcon parents appeared to have stopped nesting recently, a monitor group says.

Fifteen-year-old Madame X and her partner Surge have abandoned their second scrape, shortly after the disappearance of the couple's third egg of the season, according to Hamilton Falconwatch, part of the Hamilton Community Peregrine Project.

The intrepid pair, who have set up camp on the ledge of the Sheraton Hotel, have kept falcon enthusiasts guessing for the season.

The peregrine falcons' nesting spot is located on the side of the Sheraton Hotel's 17th floor. (Matt Moir/CBC)

“What happened? We just don't know,” said Mike Street, senior monitor of Falconwatch.

Further nesting is possible, Street said. In 1995, the city's first Peregrine chick – aptly named Hamilton — wasn't hatched until early July. Given the age of the parents, however, Street said it is unlikely it'll happen this year.

However, the news is a reason to celebrate instead of mourning, Street said.

Since 2001, Madame X has raised and fledged 40 chicks, 25 of them with Surge. Offspring from the nest now span several generations and have been spotted in five states in the U.S. — some as far away as Pennsylvania and Ohio.

“When it comes to being parents they are the exception, not the rule,” Street said.

“Instead of mourning one or more chicks we may not see this season, let's celebrate the huge contribution Madame X and Surge have made to the recovery of their species, and hope for the best next year.”

Hamilton' Falconwatch will continue to monitor the nest ledge and will announce any developments, Street said.