Herding dog nipping calves of strangers

We have a 3 year old Aussie. He is well trained, obedience class, agility, well off leash, a little herding. He nipped the new person to our house when they left. The person had spent 6 hours at our house and we kept an eye on him and he was good.

He has also nipped a kid that was running by at a soccer field. He went from a relaxed laying down to a nip.

We think it has something to do with his herding instincts. We tried a trainer that does not specialize in herding dogs. It has helped but I feel we need someone with herding dog specialty. We live in northern virginia.

my collie used to do this .....did the dog draw blood? All the neighbours were terrified of her, and this was before I rescued her.

But surely it is just the herding instinct. A moving target maybe going the wrong direction. Deep instinct .

Collie here had had no training either and settled better when spayed.

It appears his training isn't quite as fab as you think. In the case of him nipping the departing guest in future tell him to sit and "leave it" before he acts. Pretty much the same thing with kids running by tbh.

Probably , ...but instinct or not, it is going to get you into trouble if he bites (nips) some one who does not appreciate him doing so,

I don`t think you need a specialized trainer, but you do need to go back to basics with him, and teach the leave command, and until you can trust him , keep him on a lead .

Thanks for your help. He did not draw blood. He is already neutered. We are keeping on a lead in the house if a non-family member is in the house. He just heals right next to me.

Looking for how to get to the point where he behaves well on lead and when he is in heal but what to do when he is off leash in the house. When we meet a person and he is off leash, he comes back to me to wait for the okay to greet a new person. The only problem we run into off leash is if a person surprises him. He barks and then comes back to me to ask if he can greet the person. I don't like the fact that he barks first if he is surprised. He always has a correction collar on when he is off leash just in case he decides to herd / nip someone but he has never done that. We use the correction if he does not come right away but we haven't had to use it in over a year.

What's a correction collar?

Dogs bark for a reason I would rather mine bark than nip first. But what is this collar you use ?

My heeler had a tendency to do this - the way I stopped is to pick her up when folk get up to leave; they all have to leave at some point. Now I know to expect it so she is scooped up before they get up.....
Maybe you could put the dog into another room whilst your guests leave safely. This must be a better, safer option than them being nipped? At least that way you'll get no come-back

Like other posters I am wondering what the correction collar you mention does to help.

according to google this is a euphemism for a shock collar...