Intelligence Damage (Su): Any creature hit by a sirine’stouch attack takes 1d4 points of Intelligence damage (or2d4 points on a critical hit).
Using a supernatural ability is a standard action unless noted otherwise.
Some Su traits apply continuous effects, others perform something with each use.Intelligence Damage is the former, a continuously applied effect to any touch attack the sirene makes. An example of the latter would be an Aboleth's Enslave.