When Tim and Edwin Scholes were in Philadelphia for the opening of their Birds of Paradise exhibit at the Academy of Natural Sciences at Drexel University they did a radio interview.  You can listen to the podcast of Radio Times with Marty Moss-Coane as they discuss the behavior of the birds of paradise and how they captured all 39 species.  As part of the interview they broadcast some of the birds of paradise mating calls and explain how they do it.