For example, the male may repeatedly poke his head in and out of a nest hole or cling to the side of the box and do a wing-wave display, flicking one or both wings open at a moderate speed. Once both birds go into the nest box several times, they are generally considered paired and will likely use that particular nesting site. An accepting female will begin nest building shortly after they have paired. At this point, the male begins what is termed mate-feeding where he collects food and feeds it to the female. They keep in touch by calls and visual displays as they fly about the territory.
Females are in charge of building the nest.
The male follows the female closely as she forages and builds the nest. The male is close by both signaling her when it is safe to fly out of the nest box and to prevent other males from mating with her. A nest normally takes about six days to complete. All of this is dependent upon weather and individual bluebird habits. Pairs normally spend less time building nests for their second or third broods.