ID Bird call SE Melb

Hi all, I don’t know much at all about birding but since I started working from home I have managed to id some of the birds in my backyard and have come to notice their routines, it has been quite fascinating. I am hoping someone can id a bird call.

We live in south-east Melbourne. This year, over the last two or so months we have heard a very ‘loud’ bird early in the morning from about 6am (and occasionally mid-morning) with a distinctive call (deep-sounding whistle) but we haven’t seen it. I have not heard it here before. I have finally managed to record it, albeit from inside the house next to an open window, but have realised that I can’t upload the audio here, so here goes attempt at explaining it – the notes descend and in following way – bop, bop bop bop, bop bop. Sometimes it doesn’t finish the last two ‘bops’ or they are slow to follow. We have nicknamed it ‘the happy birthday bird’ as the pattern? of the call, although descending, sounds a little like the song esp with last two notes.