The eyes are truly the window to the soul, whether you're a human being, cat or parrot. They can convey so much about a bird's current mood, whether he's enthusiastically chatting away or actually feeling somewhat agitated about his circumstances. Pupil dilation isn't uncommon in talking birds.
Look Into His Eyes
If you're conversing with your bird, a deep look into his eyes might reveal some key "body language" you didn't ever notice before. The stimulation of talking often leads to pupil dilation in birds. Not only do they frequently widen their pupils, they also frequently shrink them too. Birds often quickly switch from widened to narrowed pupils all during the span of a single talking session. This is commonly referred to as "eye pinning" or "eye flashing." Note, however, that birds also regularly pin their eyes when they're feeling irritated and possibly even aggressive.
The Thrill of It All
Dilated pupils often point to a bird that's thrilled with his current situation. Many birds thrive on face-to-face interaction and undivided attention from their owners. If your bird has been waiting all morning for you to approach him for some invaluable talk time, he might not be able to contain his eagerness once it actually happens -- voila, widening pupils.
"Thrilled" pupil dilation isn't exclusive to the enthusiasm of human interaction. Birds also often dilate their pupils when they can't wait to enjoy a yummy snack or try out an unfamiliar toy.
Widened pupils in birds also frequently denote a happy and comfortable state. If your bird is in his element talking to you, his relaxed demeanor might reflect that -- and his eyes are big components there. Bigger pupils might mean that your bird feels calm and content in his interplay with you.
Upset Pupil Dilation
Pupil dilation can indeed be a good thing, but it's definitely not a foolproof sign of pleasure. Many birds signify their utter annoyance in things by conspicuously dilating their pupils. If you're confused as to whether your talking bird is happy or feeling fierce, be attentive to other clues his body might be sending you. If he's hunched over and the feathers in the back of his neck look rather tousled, he's probably not a happy camper. Attempting to touch him might even bring upon a bite, so be careful and definitely refrain from physical contact with the little guy for a while.