Boubou - Duet-singing birds from Africa

There is a bird int the African collection called Boubou. In Africa, one can hear two birds sing duets with such skill that one often perceive the song as if it came from a single bird.
This bird often vocalize in pairs, thereby creating a duet song. Its call can often intercepted in dense vegetation where male and female can sit in separate shrubbery. Suddenly, one bird gives three quick whistles, and as a fraction of a second later its answered by a rough visslig from another. The transition is so fast that one can easily perceive the song as if it came from the same bird.
Boubou (Laniarius ferrugineus) A504-505.
The birds are in Showcase 7 in the African bird exhibition.