Marylou Whitney's Birdstone, winner of the Belmont (gr. I) and Travers Stakes (gr. I) this year, has been retired after a radiograph taken Nov. 2 revealed a P-1 medial chip in the colt's left front ankle.The son of Grindstone, out of Dear Birdie, by Storm Bird, finished seventh in the Oct. 30 Breeders' Cup Classic – Powered by Dodge (gr. I), and had been scheduled to race as a 4-year-old with the Whitney Handicap (gr. I) one of his main objectives."Soundness was not an issue, but at the level of competition he runs at, we regularly take a survey of radiographs to help us monitor his physical status and well-being and help Nick (trainer Zito) plan for his future training," veterinarian Joe Migliacci said. "The most recent radiograph that I received (Wednesday) morning by Fed-Ex revealed the fracture."There really wasn't any sign that there was something wrong. We surveyed him just as we did after the Belmont and Travers, and it came as a surprise to us. Everyone is really going to miss him. He was so great to have around the barn and work with. One of the reasons I recommended retirement is that, although he could have made it back, there was a question whether he'd be able to compete at that same level."Whitney's husband, John Hendrickson, said Birdstone is still in Texas, and no plans have been made regarding his stud career."When Dr. Migliacci recommended retirement, Marylou didn't flinch," Hendrickson said. "She said she wanted to do whatever is right and best for the horse. There has been a lot of interest in him from breeding farms, but this caught us off guard."He's perfectly sound and doesn't have to have surgery if he retires. Marylou said, 'I'm not going to put him through pain just for my enjoyment.' It's very sad, but Marylou likes her horses more than her trophies. At least he's retiring healthy. We were really looking forward to running him in the Whitney, and also in the Breeders' Cup at Belmont, where he's undefeated."Hendrickson said he believed the injury occurred during the running of the Classic. "If you look at the replay when he's coming out of the gate, you can see he is striding awkwardly on his left lead," he said. "You could tell it was kind of bothering him, but that is just my observation."Birdstone is the only 3-year-old of his generation to have won three grade I stakes, having also captured the Champagne Stakes last fall. Only one other horse--Easy Goer--has won the Champagne, Belmont, and Travers.His biggest moment came in the Belmont when he denied Smarty Jones a sweep of the Triple Crown, defeating the Kentucky Derby (gr. I) and Preakness (gr. I) winner by a length at odds of 37-1. Coming off an 84-day layoff, he defeated stablemate The Cliff's Edge in the Travers, drawing off to a 2 1/2-length victory."The heart he had was beyond belief," Zito said. "This horse never gave up, and I'd have to rank him right up there with the best horses I've ever trained. And he's probably a little bit more special because of what he accomplished and what he had to overcome. He was the last remaining 3-year-old of any consequence in 2004. I'll always be grateful to him for making me part of history."Birdstone's half-sister, Bird Town, captured the 2003 Kentucky Oaks (gr. I) and Acorn (gr. I), as well as finishing second to Sightseek in the Beldame Stakes (gr. I), and was voted Eclipse champion 3-year-old filly.Hendrickson said they have had offers for Birdstone from Japan, but Whitney's response was, "You'll take my heart first.""She's committed to keeping the horse in America, and we'll price him reasonably so he will be attractive to people," Hendrickson said. Birdstone retires with five victories from nine starts for earnings of $1,575,600.