does my bum look big?

A Waggy reflecting on his looks! :D

Very good, great timing. :)

its all clear behind, we can reverse now. :-rolling

Yes good timing :)
I wonder if he thinks the bird in the mirror is a rival ?

Wagtails certainly defend a territorial all year, and this little chap spends many hours attacking and pecking car wing mirrors, he seems to have a preference for grey. Pied Wagtails have bred here for the last five years

Yes. I have also seen Chaffinches doing that.