Eye flashing or eye pinning are labels used to describe the rapid dilation and contraction of the pupils of a bird’s eye. In humans, like other mammals, papillary responses are involuntary, responding automatically to such things as light levels and some drugs. The avian eye is different in this regard, as papillary size is under voluntary control. Rapid eye flashes are apparently used in communication, as they indicate excitement.
In psittacine species with light-colored eyes, eye pinning or flashing can be quite dramatic. Indeed, the appearance can be reminiscent of the 18th century children’s toy called the whirligig, with the dark circle of the pupil increasing and decreasing rapidly. Eye flashing is more difficult to see in dark-eyed bird species such as hyacinth macaws and some cockatoos.
Eye flashing or pinning is a sign of excitement, but this can apply equally to things the bird finds positive and negative. For instance, a parrot’s eyes might flash wildly when offered its favorite treat, which indicates excited pleasure. The bird’s eyes might also flash when the bird is guarding its territory against someone or something it perceives as a threat.
Since eye flashing can be a precursor to aggression if the bird’s warning isn’t sufficient, owners should proceed with caution until more information is known. Careful observation of body language should give more clues. For instance, if the bird is giving a warning display, it raises its nape feathers (“the hackles are up”), flexes its wings and fans its tail feathers. If unsure as to the bird’s motivation, owners are wise to stay clear until the bird settles down.