How do tiny songbirds sing so loud, for so long?

The week's Quirks Question comes from Ian Guthrie in Comox, British Columbia, who asks, "The Pacific Wren is the size of a golf ball, yet has a fairly loud song that goes on for 5 to 10 seconds in what seems to be an unbroken stream.  How does it do this?"

Dr. Dan Mennill, a Professor of Biology at the University of Windsor, explains that birds produce sounds with a very efficient vocal production organ called the syrinx. The syrinx allows tiny songbirds such as the Pacific wren to produce loud, long songs in a couple of different ways.  First, almost 100 percent of the air that passes through the syrinx is used to produce songs. By comparison, we use about 2 percent of the air that passes through the larynx - our vocal equivalent - to make sound. Also, even though it may sound like continuous singing, the syrinx allows birds like this to actually take miniature breaths between each syllable of the song. The rapid replacement of air between each syllable maintains a constant pressure between the air in the lungs and the outside air, and explains why the song sounds like it is uninterrupted