Alex, a parrot with the gift of gab, dies - The African grey knew more than 100 words, breaking stereotypes about birds. He died of natural causes.

Alex, the African grey parrot who knew more than 100 words, could count to six, and recognized shapes and colors, has died. The bird was 31 and appeared to have died of natural causes, said Irene Pepperberg, the scientist who trained and studied him for three decades.

Alex's feats, which Pepperberg documented in dozens of scientific journals, challenged the notion that only apes and dolphins were smart enough to understand human language. Alex did not merely mimic words but showed that he grasped their meaning.

"He just broke all preconceived notions about bird brains," said Pepperberg, who conducts her research at Brandeis University and Harvard University.

Pepperberg, who was trained as a chemist, bought Alex from a pet shop in 1977, when the bird was a year old. Using a new technique, Pepperberg taught Alex to classify and group objects by their physical properties, such as their color or the material they were made of.

When presented with a tray of objects, Alex could identify which were blue, metal or round.

"This animal had concepts, not just labels, and some concept of numbers," said Georg F. Striedter, an assistant professor of neurobiology who studies parrot cognition at UC Irvine. Alex showed that parrots were "smarter then we used to believe."

Alex's exploits were featured on numerous science programs, including an episode of the PBS "Nature" series called "Look Who's Talking." In 1999, Pepperberg published her book, "The Alex Studies," which described her decades of research.

Some scientists have questioned whether Alex was as smart as he seemed. African grey parrots are very social birds, and some scientists argued Alex was guessing the correct answer from subtle cues he picked up from his trainers, although it was clear he was capable of making many mental connections.

"Alex's abilities were -- or should have been -- a nail in the coffin of those who maintain that there is a qualitative discontinuity between human and nonhuman animals," said David P. Barash, a professor of psychology at the University of Washington.

"The phrase 'bird brain,' still sometimes used as an epithet, is in fact a compliment. I'll miss the stubborn little feathered bastard," he said.

Pepperberg took advantage of the African grey's innate sociability, training Alex by having him watch her tell a human what to do.