@Monica im sorry... most likely wasted your time
Not at all! I only hope that you learn something!
In eclectus parrots, the females are the brighter, more vibrant birds (at least as per some people! males are just green with some red - believe me, both are stunning in person!). I've heard this is so that the females can "blend in" to the nest cavity better. (not sure if there's any truth to this)
In birds of prey, the females are often larger than the males, and it's believed they were designed this way so that the females would have more power to protect the nest from invaders. Otherwise, the males and females are identical in appearance.
In several spider species, it's often the females that are larger and more "attractive" in appearance and the males are these tiny, minute little creatures. (tarantulas being one exception)
Many parrot species cannot be visually sexed because many are monomorphic - having little or no variances between the sexes. Conures, cockatoos, macaws, lorikeets and african greys are all great examples! Cockatoos you *might* be able to tell with the eyes, but it's not always 100% accurate (could be close, though!) African greys you can tell by tails and perhaps overall color, but again, not 100% accurate. (probably less accurate than cockatoo eyes!) Birds like eclectus, cockatiels, ringnecks (not Australian variety) and a few others you can typically sex them by 2 years of age, if not much sooner. (depending on species)