Analyzing androgynous characteristics in an emperor penguin courtship call

In the emperor penguin courtship call, male vocalizations are composed of long, slow bursts with lower frequency tones than the female version. But calls of SeaWorld San Diego male penguin E-79 defied this binary. Also unusual was this penguin's male companion, E-81. The pair 'kept company' and sometimes exhibited ritual courtship displays. Researchers studied the courtship calls of E-79 and E-81, recording the birds in their below-freezing enclosure and refining the usual technique for analyzing the bursts.