Note 2 at Lk. 15:10: In the preceding parable, Jesus said there is joy in heaven "over one sinner that repenteth" which could include any or all of His creation in heaven. However, in this parable, He says the joy is in the "presence" of the angels. This would probably refer to the saints who have already gone on to be with the Lord as the ones who are rejoicing. While there is no reason to doubt that angelic beings rejoice at the new birth, it would certainly be understandable how someone who has experienced God's forgiveness firsthand would have even more reason to rejoice at the salvation of the lost.