How much space do quail and pigeons need?
Do they need flying space?
Do they lay eggs regularly like chickens and some ducks, or only when they're going to sit on them? (I'm still unsure about how that stuff works)
quail need about two square ft per bird, if it's cots or buttons. with a minimum floor space of 10 square ft. Pigeons like to be able to fly, so there loft (what a pigeon coop is called) is awesome if it's big enough for you to walk in and the it's a to fly, as well as having an aviary attached (which is where the quail would be, ideally). Pigeons do love to fly, but quail dont. If you have a 4×8 loft with 8×8 aviary that would be plenty of space to fly your pigeons, even if they never get to free fly them outside. In that setup your could keep 6 pairs of pigeons, plus a bunch of quail outside.
free flying pigeons is very rewarding, but has lots of risk and needs lots of training. I can give you a brief example of free flying pigeons and training later tonight.
pigeons lay eggs with the intention of hatching and raising them, plus, they do it ALL themselves! QUail, lay eggs nearly every day, but rarely sit. Coturnix quail have lost the instincts to sit and raise babies.

button quail are close to it, it given a good big coop and a natural setting, they still might. Mine have started to try, but aren't the most faithful of mothers.
Another question: Are carrier pigeons actually a thing?
Kinda. Carrier pigeons were used in the water to deliver messages from battles, or from station to station. They were very commonly used in WW 1, and at the start of WW 2 they weren't used. But later, they said "where are the pigeons!!" you see, the pigeons were more reliable than electronic communication, as they could not as easily be intercepted. Carrier pigeons were homing pigeons, but got named carrier pigeons because they carry messages. You an still send messages from one pigeon loft to another, if the birds are trained. How it worked in war was the soldiers would take pigeons with them, and attach a note and release them with updates. And bases would borrow pigeons to send messages to each other.I
Homing pigeons today are raced against each other, which is a very interesting aspect of the hobby, which i dont participate in,,, yet.
