Bird defending his territory (and birdbox)

Interesting things happening in my birdbox this morning! One bird (Bird1) visits the box and calls his/her partner. Another bird (Bird2) enters the box to inspect it. Bird1 flies out again. A few moments later an angry male (Bird3) enters and chases Bird2 out of the box within a fraction of a second!

7 April 2012, 7:56am

You can clearly see how bird3 makes himself look big and impressive by spreading his wings slightly, raising his blue crown feathers and fanning his tail.

7 April 2012, 7;56am

As I ‘m writing this, I see this same bird checking the bird box now every ~15 minutes or so. Every time he just peeks through the opening for a second without entering and then flies off again. I’ve also seen him singing high in a nearby tree. It looks like he now owns this territory and this birdbox.

I’m sure I’ve seen this bird in and around the box many times, but it is often difficult to tell them apart.