Hello, some advice on Robins in our garden.

Hi there, new to the group! 

Was hoping for some advice with Robins in our garden. 

So we have some robin's nesting under our back porch. Looked like they had two chicks. 

Unknown to me, the chicks had fledged and I let my dog out in the garden, I heard a noise and it was the adult robins making a awful noise trying to dive bomb my dog, went out and sadly by dog had killed a fledgling. Quickly got the dog in and have kept him out of the garden as I expected there to be another fledgling somewhere. Few hours later I was in the guarded and noticed the Robins bring food into some undergrowth that we have and saw that there was another fledgling. 

Is the dog has been kept out of the garden and I have Benn keeping an eye on the little one and the robins. I too my dog out on the lead (so he couldnt get to the other fledgling) so he could go to the toilet. And whenever I do one of the robins will keep dive bombing the dog and making a warning call from above in the trees or the garden wall etc which I gather is completely normal. 

The fledgling has been in the garden for a few days but sadly yesterday evening I went out and realised the robins were not bringing any food down too the area the baby Robin normally is, I went and had a look and found a pile of fledgling feathers and fluff, so sadly it looks like he was predated, we do have a lot of magpies and crows and the occasional jay. As sad day, but its nature. 

My question is, when will the adult Robins understand they have no young? I have searched the whole garden to double check the baby bird isn't there and it isn't, but every time my dog now goes into the garden, he keeps getting dive bombed by the robins and they keep making their warning call. They swoop down really low to the dog calling at him, I'm worried that my dog may catch one of the adults. 

Interestingly the Robins don't mind when myself or partner are in the garden only the dog. Im just hoping at some point they may forget the whole deal and let my dog go outside in peace? 

Any advice would be amazing. 

Thanks