Normally, the male would already be inside the box when the female comes inside too.
Although nest building has not yet started, we now have a pair of bluetits occupying Box2. Here they are doing a typical swap-over.
Immediately the female arrives, the male gets ready to go. In this photo we have been lucky to see both birds more or less stationary!
Off goes the male, leaving the female in charge.
The female always seems surprised by his quick exit - but that's probably my being anthropomorphic!