In Oz, birds in various types of forests and woodlands will start singing very early in the morning; the phenomenon is known as "the dawn chorus". Research by ornithologists with tape recorders has shown that all the birds in a particular area will pitch their own calls relative to the first bird that starts the calling; when a taped call is played (using a variable pitch playback) before the first bird starts, the pitch of all the subsequent chorus is varied according to that of the first call.

Perhaps the Capt.'s cuckoos have been promiscuous in their listening?

Cheers, Rowan