Early morning bird calls

Hi all,
Wondering if anyone can help identify a bird that calls at about 3-4am and continues for hours. It does several medium pitch dk (dk dk dk dk dk) sounds followed by high pitched reh rh reh rh reh rh reh rh. It seems to be calling to another bird as in between I can hear another bird repeating it in the distance. I live in Adelaide, somewhat close to the city if that helps.
Kind regards,
Jess