They build a nest from all kinds of coarse materials. They will produce 3 or 4 eggs that the female will incubate for between approximately 18 and 20 days.
Fledging occurs after 45 days. A couple of weeks after the young have left, the parents may start acting aggressively towards them so it is better to remove the young birds in good time. These birds may well produce a number of clutches per year, but you should be careful not to exhaust them by removing the nest box after the second clutch.