Help with bird identification

Hi there,

I came past a bird I've never seen today in my local area in southern Sydney. I didn't have my camera on me and despite all my attempts googling I can't figure out what it was, so I thought someone here may be able to help!

It was a largish greyish bird, certainly bigger than a magpie, more the size of a large crow. Originally I thought it was a falcon of some kind but upon closer inspection it didn't quite look like one - it had a medium-size straight beak (rather than a curved one) and didn't sit quite as upright as a falcon. The eyes looked reddish. It was perched in a low tree. As I got closer to get a look, it would shift branches such that branches obstructed my view, as if it was hiding from me. 

In trying to find out what it was on Google, it looked similar to a little wattlebird, but was bigger and seemed more grey. I also found the Australasian Bittern but that didn't seem quite right either.

Sorry, my description isn't very detailed but any ideas?

Thanks!