Mystery mystery

field recording The sound I am trying to identify is the 3/4-note all-one-tone 3 times in the recording. The habitat is prairie/ranch land. There are a few trees (the bird might be in one) surrounded by tall sunflowers, grasses and sorghum, all leftovers from other years, so they are not in rows. Overall, it is about 6 feet tall with some bare spots. Unfortunately, I have to trespass to get any closer. I have not heard this bird in the past 7 years.. . The bird calls all day long, same volume, same duration, same repeated phrases.; animal seen:no; playback used:no