I'm not an expert here, but I find this interesting enough to have done some recreational reading. What I know is that corvids and parrots have a different brain structure to mammals (they diverged about 300M years ago) but, in an example of convergent evolution, have developed areas that serve the same function as our neocortex. It's called the pallium, and has a very different organisation to our neocortex. Instead of the six layers in our neocortex they have clumps of neurons called nuclei. They also have much higher neuron density than mammals, allowing them to fit more smarts into their tiny heads :-)