Not sure, but it is difficult to imagine where these new sounds are coming from. I have never heard another bird quite like some of the sounds, one particularly

Not sure, but it is difficult to imagine where these new sounds are coming from. I have never heard another bird quite like some of the sounds, one particularly clear one sounds like "eel" but it's as clear as a human would pronounce it. He also cycles through a pattern (probably for attracting a mate) and it gets more and more complex as time goes on. He keeps adding to the noises and pattern, but it's very predictable.