We know Elves do procreate and have children. We know they do have sex. Immortal beings with normal reproduction would fill Middle-earth if left unchecked (like rabbits).
We see Elrond with 3 children in 3500 years which would be unlikely for a human.
I can only think of 3 reasons:
- Reduced sex. Elves have a reduced sexual drive (similar to Vulcan Pon Farr) so that they have intercourse only every couple hundred of years (sad sad sad life).
- Reduced fertility. Elves have sex at the normal rate but it’s really difficult for them to get pregnant so you can literally spend 1000 years trying.
- Contraception. Not so unlikely as some contraception methods are documented going back to B.C. dates.
Is there any canon source as to why there are so few Elves in Middle-earth?