For six years, a pair of black vultures lingered around Martha Midgette’s rural Southern Maryland home, tapping on the windows, snatching cat food and preening each other on the porch.

“We called that pair The Old Married Couple,” said Midgette, 74.

Midgette, a retired Navy environmental analyst, and her husband are used to seeing wildlife on their rambling 17-acre property in Accokeek, Prince George’s County, near the Potomac River. They leave out food for deer, opossums and a colony of feral cats they have had neutered and vaccinated.

But there was something special about the vulture couple, which would appear each year with a new downy-headed fledgling or two. “They were cute,” said Midgette. “They cuddled.”

Then late last month, one of the vultures arrived on the couple’s porch before dawn. Midgette opened the door to see the bird collapse and die.

Before she could figure out how to dispose of the dead bird — a tricky task given the bird flu epidemic — Midgette saw an unexpected sight. Another vulture awkwardly dragged the dead bird’s body into the yard, a moment Midgette captured on video.

Then a group of vultures gathered around the body — not to eat it, as they might do with another animal carcass — but to silently stare.

“The group stood around it,” Midgette said. “Then they were all up in a tree looking down on it. It was pretty sad.”

Vultures, despite their reputation for being rather, well, gross, are intelligent and complex birds who form lasting relationships, said Neil Buckley, a vulture expert and chair of the biological sciences department at the State University of New York, Plattsburgh.

“They’re highly social, much more social than most birds,” said Buckley.

Unlikely many species of birds, which engage in a bit of extra-nest nookie, vultures are truly monogamous, Buckley said. Moreover, they form long-lasting bonds with their young. Rather than fly off for good, young adult vultures stay near their parents.

“Vulture roosts are full of family groups, a social center for the birds,” said Buckley. “Family members hang out together. They collaborate.”

In other words, when you see a group of vultures circling around a dead deer by the side of the road, they’re likely all related.

Although vultures are often maligned as symbols of death and greed, they play an important role in the environment as scavengers that consume the rotting flesh of dead animals.

A study published last summer showed the devastating effects of an ecosystem without vultures. The use of cattle medication toxic to vultures nearly drove the bird extinct in India in the 1990s. Without vultures to pick carcasses clean, pathogens spread, dead animals polluted water sources and the population of feral dogs swelled. Nearly half a million people died as a result, scientists estimate.

The black vulture, the kind that Midgette sees in her yard, is the most common species of vulture in the Americas, Buckley said. Their population and range has increased over the past several decades, likely as a result of the profusion of roadkill, he said.

Vultures have strong acids in their gut that can neutralize many pathogens; however, they are susceptible to bird flu. Midgette said she reported the dead vulture to the Maryland Department of Natural Resources.

Buckley said it was hard to say just what the vultures were doing with the body of the dead bird. “It’s not hard to believe that the birds would be aware of this dead individual,” he said. “Beyond that you’re in the area of pure speculation.”

He noted that some mammals, including killer whales and elephants, appear to mourn their dead. “It’s reasonable to consider that lots of other animals have feelings,” Buckley said.

Vultures “are very social animals. They do have strong bonds between individuals,” he said. “I don’t think that should be underplayed.”

Back in Accokeek, Midgette said the surviving member of The Old Married Couple still appears to be reckoning with its mate’s death.

The bird continues to drag its partner’s dead body around the property, as if hoping its wings could take flight once more.