My cockatiel likes to make this short, kind sound: 'Toot'. It sounds a bit like a very short train flute. She seems to make this sound whenever I appear from another room or come around a corner. Recently she also started saying this to my two cats whenever they appear (which btw go very well along).
I suspect it means 'Hi' or something close, but I find no information on this on the web. Is it something my cockatiel has "invented", or is it a common sound? If it's common, what does it usually mean?
I also wonder if this sound is part of what is called 'chirping'? As English is not my mother language I'm not sure of what sounds are considered chirping.