screeching bird sound in lower blue mountains

Hi All

I'm new to this forum. I have just started paying attention to all the bird sounds in the area I live in - the urban lower Blue Mountains, NSW

About 7:30am every morning, a bird makes a screeching call four times in succession. I only hear it once. Sometimes it is a way away, sometimes it is close. It's as loud as a sulphur crested cockatoo but doesn't have the same tone as a parrot. It's not a Koel either. Unfortunately I haven't been able to catch a glimpse of it.

Any ideas?

Kind Regards

Narelle