Corvids. Just... Corvids. (link)
(btw did you know all modern corvids are descended from Aussie ancestors? Well, technically Australasian ones, but close enough) -- RecklessPrudence
Ravens are widely recognised as one of the more intelligent birds on the planet Earth. Substantial evidence for this includes the fact that they have learned how to tame humans.
Humans tend to object to that minor fact. They will go on endlessly about how they were the ones to teach corvids how to communicate in their language, and how they were the ones who observed them using tools, or playing with human artifacts. Or how they realised that corvids knew about trade.
The simple fact of life remains that humans have been doing all this work and building all this cool stuff and ravens have been slouching around and taking advantage of things like human expansion.
You can take either perspective you like on that one.
Ravens are cleverer than they really need to be. Your average scavenger is usually only smart enough to spot the next meal. Ravens, on the other hand, have become clever enough to spot an easier way.
This is one of the key factors in human evolution. But somewhere along the way, humans messed up and started working at things again. Whilst the ravens just hung around and decided that being amusing was way easier.
Humans may have been taught by the ravens. Simple concepts like 'barter', or mimicry as a method of negotiation. Ravens may have even shown primitive hominids how to use tools. They may have taught humans how to distract predators and steal their food.
Ravens have long since been observed riding bigger, more powerful birds. They could easily have given humans the idea of climbing onto a horse and using it to save energy.
Humans are either the ravens' greatest accomplishment or their biggest failure. It all depends on who you ask.
But if you could engage a raven in conversation, they would sigh and roll their eyes at humans as a species. At least they always have food available...
 Or, if you prefer, wing.