Voadam
Legend
Stirge :: d20srd.org
The relevant part below is bolded.
Blood Drain (Ex)
A stirge drains blood, dealing 1d4 points of Constitution damage in any round when it begins its turn attached to a victim. Once it has dealt 4 points of Constitution damage, it detaches and flies off to digest the meal. If its victim dies before the stirge’s appetite has been sated, the stirge detaches and seeks a new target.
The relevant part below is bolded.
Blood Drain (Ex)
A stirge drains blood, dealing 1d4 points of Constitution damage in any round when it begins its turn attached to a victim. Once it has dealt 4 points of Constitution damage, it detaches and flies off to digest the meal. If its victim dies before the stirge’s appetite has been sated, the stirge detaches and seeks a new target.