They usually will only mate once a day in the morning. This will go on for about two weeks, during and after which the female will lay eggs. Usually the female picks the nest site, sits on the eggs and all that, but sometimes the male helps building the nest and sitting on it. I've never heard of a male sitting on eggs for the entire incubation (though I don't doubt it has happened), but they often will trade on and off with the female.
Both the female and male will get really defensive once she is on her nest, so be careful. Their beaks can draw blood and their wings can cause serious bruising, so its best to just leave them alone until the babies are hatched, in my opinion. Just provide food and water and leave them be.