Who are the smart birds?

To understand the evolution and function of cognition, it is important to know the breadth of species demonstrating a variety of cognitive abilities. Statements in scientific and popular literature commonly assert that avian species in the corvid and parrot families are the most intelligent. However, it is unclear whether there is sufficient data from a diversity of taxa to support this claim. I reviewed research from the last 25 years to evaluate birds that have been tested for any cognitive ability. Current research encompasses less than 30% of families and 2% of species. The most studied family was Corvidae, followed by Columbidae, Paridae, Phasianidae and Psittacidae. Species from these top five families comprised 64% of studies, illustrating a bias towards these families for avian cognition research. There was also a bias in the focal species for testing different categories of cognitive ability. Traditional lab species from Columbidae and Phasianidae were primarily tested for fundamental cognition, while Corvidae and Psittacidae were more frequently tested on social cognition. This small and biased sample of focal species and cognitive abilities precludes conclusions about the cognitive superiority of any species or the characteristics favoring the evolution of certain cognitive abilities.