Can you identify this Bird?

Hi 

I was in the park the other day and I heard this bird high up in the tree seemed to be in a nest as it wasn't on any of the branches. It has happened a couple of days in a row where it continues to make lots of different sounds one after the other. Does anybody know what it might be? I just can't see anything just a nest and these sounds coming from it.

I think it is a Starling as I know they do lots of imitation sounds etc but my Husband isn't convinced.

Can anybody help please??

Thanks