As already stated in the rest of this post, you cannot visibly tell the sex of an Alexandrine until after they have their second year molt, and that's at the earliest. 2 year age minimum on seeing a black ring, but only after their second molt. Sometimes it takes up to 3 years, but never before two. I have seen so many people like the original poster of this thread that have an 11 month old Alex, ask us, we tell them that DNA is the only way, then they come back and tell us that a person at a pet store or a bird dealer looked at their 11 month old Alex and it's 100% a female because it's beak is shaped this way or its head is shaped that way...It's all total crap. An 11 month old Alex has hardly started to fill out, it has a ton of growing to do, so it's beak and head aren't even close to looking the way they will at 2-3 years... Ironically the same time their second molt will be over and they may start to develop their ring, lol.
So at 3 months old there is no one on earth that can tell you what sex your Alex is by looking at it. NO ONE!!! 3 months is a baby that has not grown enough to even get a feel for what it's beak, head, etc. will actually look like, and that is totally inaccurate anyway. Sorry, you have a little baby. There is no trick here, and the minute someone tells you that "They can tell by looking", and you listen to them, your male Alexandrine will be laying eggs!
Just go on Google, search "Parrot DNA Sexing", and go to any of the hundred labs that offer DNA sexing. It only costs like $20-$30, it's 100% accurate, doesn't hurt your bird at all, and you'll know for sure in a week or two just by sending in either a few chest feathers or a tiny drop of blood from a little toenail clip. Easy, cheap, and absolutely certain.
"Dance like nobody's watching..."