Around 1pm the female was in the box (pic 1) when a small group of House Sparrows assembled in the birch tree. She went into defensive mode straight away, spreading her tail and holding her wings out behind her (pics 2 and 3), swaying from side to side as she did so.
Several times she would fly up to the entrance, maintaining her flared tail and wings when there (pics 4 and 5). Although I could see her beak open several times she did not seem to call at all (pic 6). However, she made a great deal of noise as her wings vibrated rapidly.
In pic 7 you may just make out an object just to the right of her head - this is a Sparrow that approached the entrance as she flew up. It left very quickly and, as I watched through bino's so did the rest of the group.