well here is my story.........
First of all birds are not more important than us. God says, will I not feed you or clothe you, as I do to the birds and animals, are you not more valuable than them.
Then as for birds being angels, to some decree yes. I have many a time drove down to our beach here for serene and quiet and prayed or spoke to God and the Angels. Many times birds would land in front of me as a sign or to send me some kind of message.
One time after speaking to God, I could hear this bird chirping like he was trying to tell me something and I looked up and there he was on a branch in front of my car as if trying to get my attention. Chirping away almost talking.
When I noticed him he flew away. The message I did receive from that was that my prayers were answered and I noticed so now he could depart.
Another time I was visiting and I was sitting in a room by myself, well next thing I know this bird attaches himself to the window sideways with no ledge or anything. It actually amazed me, started chirping then looked at me and flew away.
So I am not really sure they are Angels, however I think they are messengers of angels/God. Look when the dove landed on the shoulder of Jesus as he was being baptized, it was the father/creator.
So if you have faith and this is the way God knows you will understand a sign than yes I believe they are messengers with messages.