Who’s the best $5,000 stallion on the planet? Judging by the quality of his top racers, classic winner Birdstone (by Kentucky Derby winner Grindstone) would surely ring the bell.

Sire of Kentucky Derby winner Mine That Bird and Belmont Stakes winner Summer Bird, Birdstone started like a rocket at stud, with that pair of classic winners in his first crop, as well as Brooklyn Handicap winner Birdrun.

Overall, Birdstone sired seven stakes winners from 67 named foals born in 2006, which is a bit more than 10 percent stakes winners to foals. That good percentage, along with the class they showed, propelled Birdstone past crop leader (by entering stud fee) Smarty Jones (Elusive Quality) by various methods of evaluating stallion success.

Birdstone has not maintained that level of classic success, nor has any stallion. But on Saturday, he added a third G1 winner when Noble Bird came home the victor in the Stephen Foster Handicap at Churchill Downs.

Bred in Kentucky by Jack Swain, Noble Bird is one of the revelations of the current season. To date, the 4-year-old has four victories from 10 starts. Winner of only a maiden at the beginning of the year, Noble Bird has come through his allowance conditions and then stepped up in class to finish a close second in the G2 Alysheba at Churchill on Kentucky Oaks Day.

In the Foster, Noble Bird graduated to stakes winner and G1 winner in one race, and the good-looking chestnut has already given owner John Oxley a tidy return on the $105,000 that it cost to acquire the colt at the 2012 Fasig-Tipton Kentucky July sale of select yearlings.

Consigned by Brookdale Sales, Noble Bird made a good impression on the grounds of the July sale. Strongly made, the chestnut has good length through the body, as well as a deep shoulder and a strong hip. Noble Bird also showed a presence at the sale that attracted buyers to keep looking, even in the summer heat, and when the sleek colt went through the ring, enough raised a hand to push his price above the sales average.

One of the reasons that buyers felt an interest in Noble Bird, no doubt, was that he looked like he might make a 2-year-old, with the expected further payout of mature development and improvement at 3. That had been the pattern of development for Birdstone, who won the Champagne at 2, then the Belmont and Travers at 3. Likewise, Mine That Bird had been champion 2-year-old in Canada, then improved to win his classic and to place second in the Preakness, third in the Belmont.

That pattern of development is an important factor in evaluating prospects by Birdstone and in selecting mates for him. The pattern of juvenile class, then accelerating 3-year-old form was muted in Birdstone’s sire, Grindstone. This dark brown was the first winner for his sire Unbridled, but then he was put away till 3, when Grindstone became his sire’s first classic winner.

Of course, Kentucky Derby winner Unbridled became a legendary sire of classic winners and competitors. His branch of Mr. Prospector, through Unbridled’s Belmont Stakes-winning son Empire Maker, is the line that produced our new Triple Crown winner American Pharoah (by Empire Maker’s son Pioneerof the Nile).

The other lines of Unbridled include Unbridled’s Song, which is highly sought after at the sales and is known for its speed.

Grindstone is the other principal line, and Birdstone is its chief.

Interestingly, this is the counterpart to Unbridled’s Song. This branch of Unbridled is good-sized but not overly large, and it is well-endowed with stamina, yet possessing speed.

When all the parts combine, the results can be very fine indeed. This is probably due to the horses putting together the needed traits of our historic classic types.

Gainesway’s Michael Hernon noted that “Birdstone combined the most sought-after qualities of American breeding by winning at the top level as a 2-year-old in the G1 Champagne Stakes and then carrying his ability a classic distance for victory in the historic Belmont Stakes at 3. Furthermore, he can get you a nice type so that commercial breeders with a good yearling have that opportunity as well.”

The crops by Birdstone beginning with Noble Bird were bred after Mine That Bird and Summer Bird had shown their form. Perhaps these subsequent crops will continue to expand their racing horizons and their sire’s reputation for combining speed and stamina.