Mr. Whiting produces about 80,000 roosters a year for feathers and owns specific genetic lines that guarantee long, strong feathers. Each bird has his own “apartment” where he is “truly pampered” before being euthanized and plucked, he said.

“The fashion world is a vastly larger animal than the fly fishing world,” Mr. Whiting said. “We can’t keep up with demand. Things are pretty crazy.”

The feathers, anglers said, are used to help the flies that mimic bugs that sit atop the water, which are called dry flies, as well as wet flies, which sink below the surface and are supposed to look like bait fish.

Dry flies typically use brown and neutral feathers, which women prefer for a more natural look, and flies that sink often use feathers in colors like yellow and electric blue, which deliver more pop as a hair accessory. Some feathers come in solid colors, and others have patterns of contrasting colors.

The qualities that make the feathers so attractive to anglers — pliability and durability — are also what appeal to hairdressers. The feathers can be washed, blow dried, curled and flat ironed, and typically stay in hair for a few months.

“They’re just like hair and they don’t fade,” said Sheryl Miller, the artistic director at Fringe Hair Art in Kennebunkport, Me., where three feathers cost $25.