WASHINGTON (AFP) - It is an odd tradition, to be sure. Every year, on the eve of Thanksgiving, the president of the United States "pardons" a turkey at the White House.

For the sixth time, Barack Obama did the job on Wednesday, sparing a bird at a ceremony at which he was joined by his (somewhat underwhelmed) daughters Sasha and Malia, 13 and 16.

The myth behind the tradition is that - after overexposure to the media in Washington - once pardoned, the rotund turkey will spend the rest of its happy days lolling around, far from anyone's plate. (Stuffed turkey is the classic US Thanksgiving meal.) But the reality is far less poetic.

Commercially raised turkeys have been bred to be large to feed a crowd - the massive store-bought birds can barely walk, much less fly.

They can be five times larger than the wild ones still in American forests. Commercial turkeys also have short lifespans.

Of the two turkeys pardoned last year, only one is still on the farm.

"Caramel and his cohort Popcorn arrived at Morven Park in January after spending the holidays at George Washington's Mt Vernon. Unfortunately, Popcorn died of natural causes in July," the Virginia farm where they were living said.

The White House says this year will mark the 67th anniversary of the ceremonial presentation of the turkey.

The national turkey breeders association got it going after World War II. But back then, there was no pardon - just dinner.

Nobody seems to know, however, exactly when the pardoning tradition started.

Some people say it was John F. Kennedy who was the first to spare a turkey in November 1963.

What we do know is that it wasn't until the days of George H.W. Bush in 1989, that pardoning became an annual part of White House turkey presentations.

Quite a bit of Thanksgiving lore intersects with this bird - a species native to North America that was a key food source in colonial times.

Early settlers learned to survive in the New World in part by eating the local staples such as turkey, corn and pumpkin, which they learned about from Native Americans.

People who survived harsh winters, illness and fretting over food back then had plenty for which to be grateful.

Gary Cooper, the chairman of the National Turkey Federation, raises turkeys in Fort Recovery, Ohio. He brought two big birds - Mac and Cheese, 21 weeks of age - for the big day at the White House.

"This is actually the second time. My brother Jim, in 1996, brought them here when president Clinton was here," he told AFP.

"We are the first two brothers in the history of this event to do this, and we are also the only ones from Ohio to ever bring the turkey."

"It just represents another one of the many ways that us Americans celebrate Thanksgiving, and family, and the tradition."

In a carefully choreographed media show, these high-profile birds spent a few nights at the posh Willard Hotel, not far from the White House.

British comedian John Oliver joked on his HBO show: "I am here to discuss perhaps the strangest Thanksgiving tradition: I am talking about turkey pardoning.

"There is something profoundly strange about a president making a show of pardoning one turkey to mark a holiday on which everyone, the president included, consumes an estimated 46 million birds," he said. "The whole thing is so strange."

Animal rights group PETA meanwhile has urged the Obama girls to push the president to take turkey out of the Thanksgiving equation.

On Wednesday, Obama referred to media musings about the pardon tradition, admitting it was "a bit puzzling".

"But I will say that I enjoy it because with all the tough stuff that swirls around in this office, it's nice once in a while just to say: Happy Thanksgiving. And this is a great excuse to do it," he said.

Thanksgiving is celebrated each year on the last Thursday of November.