Serious nest dispute. A new couple were inspecting the Stevie hollow, when a lone male (not Stevie partner, because they flew in a couple of minutes after this) flew at the interlopers, growled and then they both growled and flew at each other in the tree - before both landed on the ground, eyed each other, and flew into more fighting. The grass obscures the reality of the scene. I've not really witnessed such aggression and competition for a hollow before - and never seen them fighting on the ground! (very annoyed that I didn't video the interaction). The fight seemed to go on forever, but was maybe a minute or so on the ground?