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LAS VEGAS — Mariah Hillman rolled down the window of her minivan just after daybreak, ready for a six-hour stakeout in the parking lot of a Las Vegas apartment complex.

Her mission: To rescue a pigeon she had nicknamed Coolamity Jane, last spotted wearing a red, plastic cowboy hat.

In December, videos of hat-wearing pigeons in Las Vegas went viral, made national headlines and gave way to a deluge of memes — someone even created a song about the birds. To Hillman, 47, who runs Lofty Hopes, a Las Vegas-based pigeon rescue organization, the hats glued to pigeons were not a joke, but a form of animal cruelty. She became determined to find the pigeons and remove the hats.

While the internet frenzy has waned, Hillman’s dedication to rescuing the pigeons has not. She has spent hours nearly every day for more than a month looking for them. She trapped two of the pigeons, nicknamed Cluck Norris and Billie the Pidge, and brought them to a veterinarian to cut off their hats, but Coolamity Jane has eluded her.

On a recent Friday morning, Hillman leaned back in the front seat of her minivan with Edgar, a rescue pigeon and her stakeout companion, perched on her shoulder.

“Maybe today will be the day,” she said. “We’ll see.”

Edgar accompanies Mariah Hillman on a stakeout to try and capture Coolamity Jane. Anita Hassan / NBC News

Searching for clues

It’s unclear how harmful the hats are for the pigeons; they may impair the birds’ ability to fly and see predators, Dr. Robert Groskin, executive director of the Association of Avian Veterinarians, said. He added that removing the hats may also be painful for the birds.

“I don’t understand why anyone would do anything like this,” he said of those responsible. “It’s certainly potentially abusive.”

Hillman has suspicions, which she said she’s shared with police.

The Las Vegas Metropolitan Police Department did not respond to requests for comment. Previously, the department told reporters that the hats did not appear to be a police matter.

(This week, a pigeon wearing a sombrero was spotted in Reno; it's unclear whether there is a connection to the Las Vegas birds, but Hillman is advising a woman in Reno on how to catch them.)

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Hillman learned that the cowboy hat-wearing pigeons had been spotted near the University of Las Vegas in mid-December, a few days after the original videos surfaced. She knew pigeons generally return to the same places to find food, so she drove around the area for a few days, handing out her business cards and asking people to call if they spotted the birds.

At night, she studied the videos, searching for clues on where they were taken. A couple days later, while driving in the area, she noticed a gated apartment complex with eaves matching the home in one of the videos. She drove into the complex and almost immediately saw one of the pigeons, Cluck Norris.

She nabbed him a week later using a wire cat trap, a red bungee cord and bird feed. The next day, she captured Billie the Pidge the same way.

“Never in a million years did I think I would be chasing down pigeons wearing cowboy hats,” Hillman said, laughing. “I also never thought I would be running a pigeon rescue.”