I am still very inexperienced at fish keeping, and that male swordtail is the only adult male I have, but he is trying to mate 90% of the time. The only time he stops is to eat and sleep.
From what I've read, swordtails are all born as females, and some will develope into males depending on the population in their environment. This sounds strange to me, so I don't know if I really believe it or not. I would think they are born with a predetermined sex, and what they mean by "becoming a male" is that they grow a sword on their tale fin.
Surely though, 1 day old fry can't have sexual drives. Perhaps it is instict for males to try poking other fish with their swords. The adult male does this, despite that the sword isn't his sexual organ. When he gets really worked up, or frustrated(?) chasing the ladies, he'll sometimes jet 1/2 way across the tank in reverse. He's quite entertaining.
To see such a young fry doing this just makes me think they are indeed born as the gender they will be. The 2 fry I already had in the fry tank are about 1 1/2 weeks old, and they haven't been doing this at all. It must be a male behavior.
If I'm right about this, my fry will end up being 3 females and 1 male. We'll see in a few months.