The E/S ratio (also known as Cuvier's fraction) for small birds is about 1/12, where E equals brain weight and S equals body weight. In other words, a small bird's brain is about one-twelfth the weight of the bird's body.
For humans and mice, the E/S ratio is about 1/40, meaning our brains make up a smaller fraction of our overall body weight than birds. Some suggest this could be a good indication of a bird's intelligence. I prefer to leave it up to this video.
Watch Alex's mastermind bird complete what he believes is one of the most complex tests of the animal mind ever constructed - and the world's first bird to do so.
Don't worry, 007 was not hurt during the making of this video.
Read more about E/S Ratio and Mammal Intelligence.