unless you want a bloody mess don't just put a strange bird in with a cock bird, at least let them see each other thourgh a divider to protect the bird if fighting breaks out. which is pretty common when you throw two birds together that don't know each other and the hen is still thinking of what she considers her real mate.
These birds have been together for about 2 months in a loft
So they have been around each other just not mated with the ones I want them to. So they won't be strange to each other. And one hen's cock was lost so now has no mate. We will see how they get along.
Is this a good time of year to mate them?
They most likely will stay paired, especially if her previous mate has taken a new hen. However, when you put the pair back into the original pen, she may try to claim her old nest box. Her new mate will follow her and fighting will ensue between her old mate and and the new one.
Well,if a pigeon (irrespective of sex) stays alone for a while,it in most cases readily accept any new partner. Pigeons are very sexually active and can't stay without a mate for long. So best is to separate them,keep them alone for a while then pick a partner for them who also a loner and then put them together in a large cage/pen or 2 sectioned pen with see through partition. (Sorry I didn't read all replies above.)
When we split a pair and re pair one of the birds(say hen) with some other bird,then her original cock will chase her and try to impress her if he's not paired with another hen.
Those pairs who are together for many years may get back together when they come across in a same loft but they will raise their current clutch with their present mate and will also flirt with their ex-mate. And they may get back together when the squabs wean and they are ready to start over again.
But USUALLY PIGEONS STAY WITH THEIR CURRENT PARTNER AFTER THE PAIR LAYS EGGS and they won't allow their ex-partner to fool around.
Ones who separate birds every molt/winter season and rejoin them with other partner,their birds stay with their current partner without having a longing for ex-mate.