The old adage about the early bird getting the worm didn't take into account the advantages of early avian home renovation.
The urban bald eagle couple that earlier this year caused a stir -- successfully fledging a chick in clear view of passers-by within Pittsburgh city limits on a hill in Hays above East Carson Street -- are at it again.
Bicyclists on the Three Rivers Heritage Trail near the Keystone Iron and Metal scrap yard have recently watched the birds building a new nest not far from the original, which partially collapsed during fledging.
Wildlife watchers wondered if November might be a bit early for nest building. But ornithologist Bob Mulvihill of the National Aviary on the North Side said science knows very little about bald eagle behaviors in this part of their range, which stretches across North America.
"We've studied eagles up at Pymatuning and in the Susquehanna River drainage, but eagles around [Pittsburgh] are something relatively new. We don't know a lot about them."
The juvenile eagle was hatched April 15, fledged in June and left its parents in late August. The adults have not migrated from the nesting area overlooking the Monongahela River. Mr. Mulvihill said they're likely to remain through winter if the river does not freeze over and fish continue to be available.
If food acquisition becomes difficult, they would likely travel together southward until they find open water.
"This time of year, eagles can be very sociable," he said. "At Pymatuning and other places, they can congregate in groups of tens or hundreds."
The eagles were first noticed soaring over the hillside near the Glenwood Bridge in fall 2012. Mr. Mulvihill said the recent nest-building activity might not be out of character for this pair.
"They did a good job as a new nesting pair, but they built their first nest in what seemed to be an odd location," he said. "In fact, it did partially collapse. The new nest is a handsome nest more fitting in an eagle-sturdy tree. These birds have some innate behaviors, but they have a tendency to learn as they mature.
"Building in the fall may be this pair's preference, or this might be what eagles do in this part of the range."
Sharing the work of nest building may be more than just remodeling. Mr. Mulvihill said the cooperation is classic courtship behavior.
"They'll putz around with it like a married couple working on the house -- it never ends, in a way," he said. "They'll work on the structure -- it's pretty big already -- and mating will begin in January, maybe a little earlier [than in 2013]. The female will line it with soft materials when it's time to lay eggs."
This year, another bald eagle couple completed its second year of successful nesting on private property in Crescent, and another pair attempted but failed to take over a red-tailed hawk nest in Harmar. The success of Pittsburgh's urban eagles, confirmation of 235 additional nesting sites in Pennsylvania and other factors contributed to the state Game Commission's decision in September to remove bald eagles from "threatened" status. They remain protected by state and federal laws.
With the Thanksgiving holiday drawing the nation's attention toward another bird, it's worth noting that Benjamin Franklin didn't much like the idea of the nest-stealing, food-robbing eagle becoming the national symbol of the United States. He lobbied for the wild turkey.
Last week, Mr. Mulvihill watched an immature bald eagle soaring over the West End Bridge spanning the Ohio River. It prompted a posting on his Facebook page.
"I think bald eagles are here to stay," he wrote. "Nice."
John Hayes: email@example.com or 412-263-1991.