I don't see any reason for the biological mother to be required to notify the biological father if she's having an abortion.

I *do* see a need for her to notify him of the pregnancy (or birth) in a verifiable way if she wants to be a single mother who potentially collects child support from him. In that case, there should be a "grace period" (window of time) during which the father may choose to sign away all of his future rights/responsibilities as a parent.