notice the interior of its mouth is entirely black, reminiscent of the black mamba snake (a highly venomous species) which takes its name not from the colour of its scale but from the colour of the interior of its mouth.
Luckily nature has not yet install a pair of fangs on this guy and arm him with venom. Otherwise he would be more dangerous than the black mamba. For the time being, he can only sings and not bite :)
Seen here singing a love song on a open perch, a rather uncommon sight. Usually he prefer to sing songs under the thick cover of tall reeds which the female love to hang around.