The control system involved a lens at the front of the missile projecting an image of the target to a screen inside, while a pigeon trained (by operant conditioning) to recognise the target pecked at it. As long as the pecks remained in the center of the screen, the missile would fly straight, but pecks off-center would cause the screen to tilt, which would then, via a connection to the missile's flight controls, cause the missile to change course. Three pigeons were to control the bomb's direction by majority rule.
Although skeptical of the idea, the National Defense Research Committee nevertheless contributed $25,000 to the research. However, Skinner's plans to use pigeons in Pelican missiles was apparently too radical for the military establishment; although he had some success with the training, he could not get his idea taken seriously
Related: bat bombs: a World War II proposal to drop bats carrying tiny incendiary bombs over Japan.