Mynahs attacking juv. Red Wattlebird

This morning a fledgling Red Wattlebird flew with its parents into a palm tree in my yard, very high up.
I was luckily outside at this point and noticed at least 6 indian mynahs constantly attacking this wattlebird. The parents were defending as best they could, but the mynahs outnumbered them.

This is the first time ive ever seen agressive behaviour by common mynahs. I used to think it was a myth and that the Noisy Miner was actaully more agressive towards other birsd - but this settles the case.

They were jumping on the wattlebird, pecking him and almost pushing him from the branch.

He managed to find a little nook to settle in, all the while the parents are not only trying to fend off mynah's, but also feeidng the youngster. So i went inside thinking he was safe for now.

Came back out and he is gone. I can hear his little chirp from somewhere but could not pinpoint it. Thought it was over the neighbours fence, but then looked behind a piece of wood i had leaning against the fence and there is the juvenile wattlebird on the ground. I picked him up (much to his dislike) and placed him into my mandarin tree which provides much more shelter for him.

By this time I'm ready to wage war on the mynahs, and I am not one to support the killing of any animal, but this is not on. I was throwing small balls from the palm tree at the mynahs but didnt make one hit. The aim is just to knock them to the ground so i can pick up and take to vet for euthanasia. didnt quite go to plan though!

I think the little one can still fly, i am pretty sure he went out of the yard for a few moments then came back to the mandarin tree where the parents are now feeding him. The mynahs know he is still around as they are hanging around, waiting for him to come out into the open again.

I am now convinced that mynah's need to go, they just can not do this to our struggling native birds.

Any advice on dealing with this? I am now paranoid that this wattlebird is going to get injured but i cant sit outside all day watching him.