THURSDAY, Aug. 6, 2009 (HealthDay News) -- Rooks aren't birdbrains, research shows.
A U.K. study found that the members of the corvid, or crow, family can use stones to raise the level of water in a container to bring a floating worm within reach of their beak.
All four rooks used in the study showed a high degree of accuracy, using only the exact number of stones needed to raise the water level to put the worm within reach. Instead of trying to get the worm after they dropped each stone, the rooks estimated the number of rocks they needed before they started dropping them into the water container. Only when the time was right did they retrieve the worm, the study authors noted.
In addition, the rooks selected larger stones over smaller ones to raise the water level more quickly. The study appears online Aug. 6 in Current Biology.
Orangutans are the only other type of non-human creature known to complete a similar task.
"Corvids are remarkably intelligent and in many ways rival the great apes in their physical intelligence and ability to solve problems," study author Christopher Bird, of the University of Cambridge, said in a news release from the journal's publisher. "This is remarkable considering their brain is so different [from] the great apes."
Though the study showed they're capable of doing so, rooks don't use tools in the wild, the researchers added.
"Wild tool use appears to be dependent on motivation," Bird explained. "Rooks do not use tools in the wild because they do not need to, not because they can't. They have access to other food that can be acquired without using tools."
The Royal Society for the Protection of Birds has more about the rook.