Only the male Loon yodels, and the yodel is his territorial vocalization. Apparently each male yodel is distinct and can be used like an audible fingerprint. To yodel the Loon fully extends its neck and enlarges the throat in order to create a type of percussion chamber. It then presses and moves its tongue into the roof of the beak to help make the pitch changes during the yodel. It is thought that as the Loons reach full size their yodel pitch lowers as the throat volume increases. During one of the many hours Deb & I spent in a canoe with Loons this summer, we observed a new male fly into the area of the pair we were watching (presumably to fish) which caused the resident male to immediately head towards the 'intruder' and start yodeling. The visitor left as quickly as he came and headed off elsewhere to fish. Here is a shot of the yodeling male. Its amazing how loud the yodel is from 30'
