Your Barred Owls are behaving in classic fashion. They'll roost and nest in close proximity to people. Cherish them. They'll keep your rat population down.
1) is it normal for them to hang together like this during the day?—Yes. Mating pairs roost together.
2) how big is their territory (and is it just one pair to an area)?---Hard to say as evidence varies. Some estimates go to about 200 hectares per breeding pair, but the owls have a great deal of overlapping territories. The reason they call to each other is to declare their territory.
3) do they leave the area at all during the winter (we only heard one hooting during the winter while now they usually answer each other)?---Some disperse, but most stay within the breeding territory, although they're not as defensive as during nesting season.
4) if the female is going to nest, when will she start and will her first choice be the place she nested last year?---Barred Owls in Southeast Texas can begin nesting in December, although most will probably nest in March. Most males begin staking out territories in January. Many breeding pairs show fidelity to original nest site for several years in a row.
5) how far away will their offspring go when grown (and do they establish their own territory)?---Yes, they'll establish their own breeding territory. Some first year non-breeding birds may remain near their parents.
