Involving birth fathers in the adoption process is imperative. Just because the birth mother is no longer in a relationship with the birth father is not a reason to not encourage his participation. In addition to his legal rights, it is also important to welcome him into counseling and encourage him to share educational, social, and medical history.
Determining the birth father’s rights may be a complex process. The identity of a birth father may be unknown to the birth mother, or the birth father may not be involved in the adoption process in any way. The birth father’s consent to the adoption or court-ordered termination of his parental rights may still be required. The specific facts in a particular situation will determine his legal rights, if any. It is possible that a birth father will refuse to consent to the adoption or take legal action to disrupt the adoption plan. If this occurs, it is possible that the child may be removed from your care. His rights depend on the laws governing the adoption.
This link provides a brief look at the varying laws each state has regarding adoption and birth parent rights.