There really is no reliable way to visually sex a Sun Conure, guessing usually doesn't work well...They are sexually-monomorphic, but the visual differences are so subtle that you usually cannot tell at all, and include things like their overall weight as an adult, the length of their legs, and a few coloring characteristics that can actually go either way some of the time, so it's not reliable etc. So it's really difficult to tell, and usually when people guess they're wrong. When I bred them I always had them DNA-tested to be sure because you just don't know....And most of the little "tricks" and "tips" you'll find online as to how to tell them apart aren't reliable at all...