Binki
Songster
I have watched many Dog Whisper.
But you see, I trained him with my birds, When I first got them he would chase, but after we gave him some sharp NO's and training, he NEVER touched them.Not once in 7 years.Till now.......
That's great, it's possible that the dog has been pushing boundaries by staring intently like a predator (should be interrupted) and only the snapping/biting is being addressed.
As you know with your flock, rank is constantly changing and if you aren't on top of the dogs behaviour (because he listened for quite a while) then it could get worse until he tries to kill.
It's even possible your deceased cat was outranking him and keeping him in line somewhat, there have been a few dogs on the show whose behaviour changed for the worse once the house cat (who was alpha or at least a constant challenger) died.
For those dogs, because there was a gap in the pack order that the humans didn't fill, the dog filled it, thinking it's the leader now leading to unstable and fearful/aggressive behaviour.
If some quick training and sharp "no's" worked the first time, I would try that again, as it seemed effective the first time but now pack dynamic could have changed to where the dog isn't taking you as seriously now.
If that's the case then you'll need to work with the dog to reinforce the fact that you are alpha, claiming its food, etc. the psychological humane ways that a dog understands is dominance.