I'm not a fan of an anthropomorphic approach to wild animals, be they mammals or avian species. Wild birds, for example, do not have personalities. What they do have is traits. In the frenzy around a bird table or feeding station, an individual Blue Tit may seem the more confident, perhaps even aggressive. I have seen plenty barge a Great Tit out of the way to get to a string of peanuts and a Blackbird (a giant by comparison) will usually give way to a smaller, more strident bird. But that is not personality; rather, it is behaviour borne of necessity (perhaps the little tit hasn't fed for some time or has a nest of screaming infants at home) or a genetic blueprint over which it has no control. Having said all that, I am now going to risk contradicting myself by going all anthropomorphic over this Greenfinch, which seems to me to be decidedly cross as if it has been disturbed mid-meal. I adore how the combination of the glaring eye and crossed beak working hard on a sunflower seed combine to lend it a rather grumpy demeanour.
Canon 1DS MkII, 1/60 sec, f8, 400mm at ISO 800mm