In 2009 Aesop-style experiments, the corvid that dropped stones into water to raise a worm was the rook.
The study recreated the central problem in “The Crow and the Pitcher.” Captive rooks faced a clear tube containing water and a floating worm that was out of reach. Stones were placed nearby, and the birds dropped them into the tube, raising the water level until they could obtain the food.
Rooks are members of the corvid family, which also includes crows, ravens, jackdaws and magpies. The result does not prove that the birds understood the fable in exactly the human sense, or that they consciously planned every step in advance. Researchers have also emphasized the role of prior experience and trial-and-error learning in similar tasks.
A common mix-up is to answer “crow,” because the experiment was inspired by Aesop’s crow. The tested birds, however, were specifically rooks, a distinct corvid species closely related to crows.