Interesting article from National Geographic, erporting on a study to be published in Science magazine:
Crows as Clever as Great Apes, Study Says
Crows as Clever as Great Apes, Study Says
They say that, while having very different brain structures, both crows and primates use a combination of mental tools, including imagination and the anticipation of possible future events, to solve similar problems. They base their argument on existing studies.
Emery and Clayton write, "These studies have found that some corvids are not only superior in intelligence to birds of other avian species (perhaps with the exception of some parrots), but also rival many nonhuman primates." Increasingly, scientists agree that it isn't physical need that makes animal smart, but social necessity. Group living tends to be a complicated business, so for individuals to prosper they need to understand exactly what's going on. So highly social creatures like dolphins, chimps, and humans tend to be large-brained and intelligent.