Geez excuse me for posting my experience here. Yes, I'm talking about my aro. which is pretty dam aggresive toward anything near his tank not some chicken sh*t skittish aro. And NO my aro has never eaten a bird but it does aggresively track the birds movement thru the glass, maybe its instinctive behaviour, IDK. I've owned a bunch of aros, silver, jar, black, etc. so its safe to say I can tell the difference between running scared, stalking prey, or protecting its territory. This same aro. (I call him The Beast) also trys to attack my dog when it gets too close and also loves attackin me when I change water.
BTW, anyone else ever seen their aro puff its mouth pouch at yah or hear it growling before? Oh wait thats just BS too so nevermind.