A strange altercation

An altercation took place between a Northern flicker and a starling in the park Friday morning (pardon the dark photos - it was a dark morning). The flickers hang around that dead tree a lot, but suddenly that day a starling was harassing the flicker quite unmercifully. Every time he got close to the cavity, the starling dove on him. After a few minutes, the starling just stood on the branch and ran at the flicker, who would retreat despite his size advantage. Finally, the flicker gave up and flew away, leaving the starling triumphant (boo hiss) on the branch.

I couldn't guess what was up - did the starling think the flicker was a nest robber or something? - but one of my coworkers suggested that the flicker may have wanted to nest in the cavity himself. A quick check over at the Cornell Lab site shows that it's up in the air which flicker chooses the nest site, and now I think that is probably right. For all I know, this is where the flickers have nested in the past; starlings are horrible at crowding our native birds out of their nesting sites, after all.