The noise originates out here somewhere...
Almost every night since we moved to the Azores, I have heard a bizzarre sound coming from the undeveloped land near our home. It occurs about an hour after nightfall. It goes on and on for a few hours and then dies down in the middle of the night. The sound is too hard to explain. I thought maybe it was a strange frog making the noise, but it didn't sound like any frog I had ever heard. One of my neighbors who just moved in as well thought it was someone playing with DJ equiment.
Finally, another neighboor got the bright idea of just asking the locals about it. She lives on the other corner of the undeveloped land and hears them every night as well. The locals immediately knew what she was asking about, and they said it was the Cagarro (ka-GAR-oh). I had never heard that name before, so I did a quick google search. To us English speakers, the Cagarro is known as the Cory's Shearwater. It was a bird!
The Azorean Cagarro... a.k.a. Cory's Shearwater
The Shearwaters are medium-sized seabirds closely related to petrels and albatrosses. They feed on fish and molluscs and can dive up to 50 feet (15 meters)! They are said to be silent at sea and raucous at night in their breeding colonies, which is apparently what we have right next door. I've tried to find the colony once, but the land is covered with thorny brambles and low growing, dense shrubs... a pretty darn safe place for a breeding colony.
So here is a great video that lets you hear what I hear every night. Imagine drifting off to sleep with this!
The crazy night call of the Cory's Shearwater