Band-backed Wrens (Campylorhynchus zonatus) almost never "sing" alone - if you can call what they do singing! Actually it's one of my favorite Costa Rican sounds, but singing? They love to duet, and a pair can sometimes sound like 40 birds chattering away. They generally occupy the higher reaches of river and stream galleries.
Douglas Von Gausig (recordist; copyright holder), Naturesongs.com
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