In 2002, researchers were stunned when a New Caledonian crow named Betty made a hook tool to solve a complex physical challenge: she used leverage and manipulation to bend a wire into a hook perfectly designed to lift a bucket to the top of a tube and bring a treat within beak distance.
Since 2002, there has been a diverse set of investigations into avian intelligence. Many of the investigations focused on the relationship between brain activities and behaviors associated with intelligence.
For example, it is well known that the hippocampus is engaged when two components associated with intelligence testing, memory, and spatial relationships, are required for problem-solving. A human who excels at the game, Concentration (a game that requires remembering where specific cards are located face down), would be no match for a bird that makes hundreds or even thousands of flights stashing seeds that later will be retrieved when food is scarce. This skill requires a highly developed ability to use spatial memory. Not only do the birds remember the approximate location of the food but remember specific landmarks that pinpoint the exact location (for example, if food is stashed and later buried by snow, and a stone used by the bird as a landmark is secretly moved, the bird searches a location that is moved by the same distance and direction as the stone).
Human intelligence historically has been measured by the Stanford-Binet Intelligence Test. Recent refinements distinguish between analytical and creative intelligence, general and specific intelligence, and a variety of other subcategories. Evaluating avian intelligence has no universally accepted tests but research into the problem-solving abilities of birds has revealed that birds surpass humans in many dimensions of problem-solving. A recent line of research uses advanced technologies to discover what connections among different parts of the brain activate, and in what quantities, during specific problem-solving events.
For example, research suggests that a small hippocampus in a bird may be as powerful as a much larger mammalian hippocampus. The reason likely is that brainpower is not directly related to brain size. It is the number of, and interconnections among, neurons that powers the brain, not its size. A parrot has as many neurons in its walnut-sized brain as the macaque monkey has in its lemon-sized brain. Indeed, the small brain size may have advantages not available in larger brains. There is strong evidence that short connections between specific parts of the brain allow birds to make faster decisions and discriminatory perceptions than occurs in mammals with larger brains.
While there is no universally recognized IQ test for humans to say nothing of other species, there are intelligent behaviors that can be compared. Birds are as adept as primates at solving certain problems. For example, adapting to unexpected changes in the environment, planning ahead, considering another's state of mind, and recognizing individuals within a species as distinguished from other members of the same species. An example of using a combination of these skills is a bird may stash food and upon departing catch another bird observing. The bird hiding the food later will return to move the stashed food when the observing bird is clearly absent.
So the next time you hear someone refer to a shallow or ignorant person as a bird brain, refer them to Jennifer Ackerman's The Genius of Birds for a lesson in humility.