Gouldian finches have different colored caps, most of the time they prefer to mate with a mate who has a matching colored head (red, yellow or black).
But if you cover the right eye of the brunette male finch he will flirt with red heads and blonds. He also made much less of an attempt to woo the female with whom he was flirting.
Birds have less of a connection between sight and the right and left brain, each eye strongly links to the opposite side of the brain. We are finding creatures that have strong eye separation also have a stronger separation between what each hemisphere of the brain performs.