I'd say that the bird is simply acting on instinct:
Mate injured,
take care of it
wow, sounds like a reaction we'd all have if our mate was injured too.
some birds mate for life so if they lose their mate, they never find another. not sure how you want to look at that but i think that goes against instinct since its in every animal's instinct to breed and further it's species. i would think it would go against instinct to not seek another mate if they lost their one and only mate.
penguins do this for example. i believe parrots do as well.
i think people dont give animals in general enough credit for having the ability to have feelings and emotions.