1 Egg a Day. Fertile?

[laurenseggs]

I have 3 hens and 1 rooster. My hens lay mostly 1 egg a day and my broder hen will always try to lay on them.
My rooster is super small compared to my Rhode Island Red and Barred-Rock hens. Like, he'd have to step on a stool to get any mating done. (but who knows? Maybe it works?) My third hen, I have no idea. She's small like him though. I just have chickens as pets, so I'm not sure or into exact breeds. However, upon looking some up, she's like a Brahmas-Ameraucuna. Idk, y'all get it?
Anyway, I hatched one chick one time from my B-A hen. She actually had 2 developing chicks, but one died.
So I know something is going on, but i took a wild guess that those eggs would be fertile. How will I know if the other hens eggs are?
The lay one a day, so idk how to tell without guessing/seeing what happens?

 

[laurenseggs]

Thanks for the help everyone.

 

[scbatz33]

Crack it open. If it has a "bullseye" it's fertile. I periodically check my hens if I change roosters or if they are new layers to see they are getting bred.

It's the only way I know unless you throw everything in the incubator.