Macy's, whose annual Manhattan parade is a cherished Thanksgiving tradition for millions, is starting a new holiday ritual: It's asking its employees to show up for work.

Pressured by competition, a shorter shopping season and lackluster consumer spending, at least a dozen U.S. mega- retailers are opening for the first time on Thanksgiving Day, such as Macy's, or opening earlier that day than in previous years. They are following Wal-Mart Stores, the largest U.S. employer, which has been open for business on Thanksgiving for more than 25 years.

"Another holiday bites the dust in favor of retailers," Candace Corlett, president of New York consulting firm WSL Strategic Retail, said in a Nov. 12 phone interview. "Our culture now is to shop, and to get the best deals. Thanksgiving as a day of rest was another culture, another time, not today."

The expansion of hours will take more than a million employees away from their families during the holiday. Organized labor has been encouraging low-wage employees to join unions for years to stem membership losses, and now wants to use the Thanksgiving hours to encourage workers to band together to improve working conditions.

"It plays into the larger themes that we've been pushing around low-wage workers who don't have a lot of job security," Amaya Smith, a spokeswoman for the AFL-CIO, said in an interview. "Thanksgiving, Black Friday is one example of one holiday but throughout the year this is an ongoing issue. These workers need to have a voice on the job."

The stores say they are simply giving shoppers, and employees, what they want. J.C. Penney and Kohl's Corp. will join Macy's opening for the first time on Thanksgiving.

Opponents of the holiday work schedules have online "Save Thanksgiving" petitions.

Martha Sellers, a Wal-Mart cashier in Paramount, Calif., says she's risked her job to protest for better pay and working conditions at the world's largest retailer. Working on Thanksgiving Day only hardened her resolve.

"Workers are going to be in that store all day Thanksgiving," Sellers, 55, said in an interview. "Wal-Mart claims it's such a family-oriented business and they're taking away the family holidays."

Wal-Mart associates, as the store's hourly employees are called, are given the option to be off on Thanksgiving or work for holiday pay, 25 percent good-in-December store discounts and free hot meals during breaks, said company spokeswoman Brooke Buchanan.

"A lot of folks really enjoy it because of the benefits they get," Buchanan said in an interview.

Sellers refuted that version.

"When you're scheduled, you work or it's a missed day," Sellers said. "So many missed days and you're fired."

Holiday shifts at Macy's, where some employees are members of the United Food and Commercial Workers union, will be staffed by people who volunteer to work and some temporary workers, according to Macy's spokesman Jim Sluzewski. They will earn overtime pay and be provided with free meals.