Several outdoor cats come through "my" yard regularly.
When the females are in heat there is pandemonium around here.
Loud, eerie yowling! Cats chasing each other up trees or onto roofs!
Hissy fits with real hissing.
Violent fights, with two cats locked in battle.
Here in the photo, two even crouched outside my window screen, growling and staring each other down.
I chased them away before the fur could fly.
(Linking to Camera Critters, still going strong after eight years.)