Alex the parrot : no ordinary bird
(Book)

In studying the intelligence of animals, most scientist had come to the conclusion that the bigger the brain, the greater the intelligence, so much work was geared towards apes, dolphins and other large animals. In 1977 a graduate student named Irene Pepperberg did not believe this to be true, so she bought an African Grey Parrot which has a brain the size of a walnut and began to train him teaching him to count, add, and subtract, to recognize shapes, sizes, and colors and to speak and understand hundreds of words. She worked with this parrot she had named Alex (Avian Learning EXperiment) for over 30 years. They became popular all over the world and people were amazed at his intelligence. They also became very good friends even giving what seemed to be parting words of love.