[What you need to know to start the day: Get New York Today in your inbox.]

Some bet as much as $200. Others wager as little as breakfast or a beer. The real prize — bragging rights and status — goes to the owner of the bird that sings the most vigorously during the competitions that kick off at dawn on Sundays in parks in Brooklyn and Queens.

The male chestnut-bellied seed finches are judged on how fast, and how long, they sing when held beside each other in cages, stimulating their instinct to establish dominance.

But this avian twist on “America’s Got Talent” has also fueled an illegal cottage industry: the smuggling of finches into the United States from South America.

Last week, a 39-year-old Connecticut man was charged in federal court in Brooklyn with smuggling nearly three dozen finches from Guyana into the country through Kennedy Airport. The 34 birds were nestled into plastic hair curlers and placed in carry-on luggage, which was selected for a spot inspection, according to court records.

Mr. Gurahoo was freed on a $25,000 bond, posted by his uncle, who lives in Queens and told the judge he is originally from Guyana. Mr. Gurahoo’s lawyer, Eric Pack, had no comment.

The contests, known colloquially as “bird races,” are especially common in Phil “Scooter” Rizzuto Park in Brooklyn.

“This is like a sport from back home,” said Ray Harinarain, a bird importer who lives in the Cypress Hills neighborhood of Brooklyn. “People from Guyana move here and bring their traditions.”

Champion birds bestow status on their owners and can increase the value of the finch — “like a racehorse,” Mr. Harinarain said.

Under federal law, transported birds must be quarantined for 30 days to ensure they do not carry avian flu or Newcastle disease, which can infect humans and domestic poultry, said Paul Calle, the chief veterinarian and vice president of health programs at the Wildlife Conservation Society. That inconvenience, coupled with a superstition that birds from the wild are more virile and better singers than birds bred in captivity, feeds the market for smuggled birds.

“Some people just prefer to smuggle,” Mr. Harinarain said.

“It’s an underground thing,” he added. “People don’t want to talk about it.”

All 34 birds discovered last week were alive, and placed in the custody of the United States Fish and Wildlife Service, which has regulations that allow for their return, if feasible, to Guyana.

The manner in which the finches are often smuggled — with no protection from high or low temperatures, no food or water and limited ability to move — creates stress, making the animals more susceptible to shedding any virus or parasite they might be carrying.

“With a multibillion dollar U.S. poultry industry, there’s a lot at stake and a lot at risk if they’re moving animals like this,” Mr. Calle said. “It’s a terrible thing.”

Though chestnut-bellied seed finches, with obsidian-colored wings and rusty breasts like robins, are not a threatened species, their illegal importation also poses ecological risks.

The finches’ robust numbers in their native region could decline to the point of collapse, as happened around the turn of the 20th century in North America with the once-ubiquitous, now-extinct passenger pigeon, said Susan Elbin, director of conservation and science at New York City Audubon.

Or, just as European starlings were introduced with good intentions into Central Park in the 1890s, only to quickly spread across the continent, displacing multitudes of native birds, exotic animals run the risk of establishing themselves and becoming a harmful invasive species.

“The problem is: They could die out, or they could do well,” Ms. Elbin said.

Donald Bruning, an ornithologist who worked at the Bronx Zoo for decades, said smuggling undermines the businesses of legitimate breeders. And the mortality rate for animals brought into the country illegally is abnormally high, he said.

He also noted that the practice may be completely unnecessary: There are far better ways, he said, to groom a champion finch than by plundering wild populations.

Baby finches, he said, learn to sing by imitation. Mr. Bruning, who was instrumental in the passage of the Wild Bird Conservation Act of 1992 that safeguards exotic bird species from being harmed by international trade, suggested competitors record the songs of champion birds and play them for chicks raised legally in captivity.

“That would solve the whole problem,” Mr. Bruning said.