well you can easily go and check or ask someone else to. if it has laid an egg i recommend you not to interrupt it because they can be very protective.

I have 4 pigeons in my garden. They live in this big bird house they have this little private area where they like to sleep and the other part is where they eat and play etc but this one bird doesn't come out much it only comes out when it wants to eat but then it goes back in. The other 3 are fine. So I was wondering has it laid an egg?