How to refer to my birth father

Hi! I recently connected with my birth father and I have a great relationship with my adoptive parents. However, my birth father and I were both so enthusiastic and excited about building our new relationship! I call my adoptive dad, "dad" and like you said I can't imagine calling anyone else that. So I call my birth father "father" or "daddy". He calls me "daughter" or "babygirl". You can find a name that feels comfortable for you that means father like father, pops, papa, pa, etc.!