I've already covered some specific birds such as storks, eagles and the Phoenix, but other birds are spiritual symbols also.  In general, birds are considered messengers of God or Being of Light.  Seeing a bird in a dream, or seeing a bird in your yard that is rare is probably a symbol you should pay attention too.  Birds generally are symbolic of the soul and of transcendence from physical to spiritual.  Large birds are often associated with the sun.  Birds are often seen in trees so they are associated with tree symbology, particularly the Tree of Life.  Mythological heroes are often accompanied by a bird who usually advises them is some way so symbolizes their spiritual side.  A bird on a pillar or fence post can symbolize the union of matter and spirit.  Jesus as a small child is often depicted with a bird.  The ancient Egyptians believed the KA (soul) left the body in the form of a bird that flew to heaven.  The dove is another bird often used in religion as a symbol of spirit, enlightenment or peace.  The Bluebird of Happiness is a symbol we are all familiar with.  The believe that the bluebird symbolizes happiness and contentment goes back thousands of year and is common in many parts of the world.  Perhaps because blue is such a spiritual color.  Many songs have been written about birds and some even mimic the bird songs.
    Bird symbols are not always positive, of course.  Crows, ravens, vultures and blackbirds are often believed to symbolize death, illness, or Satan, but not always.  Many Native Americans consider the Raven a good omen.
    A personal encounter I had with a bird occurred a few years ago.  One summer day, Saturday or Sunday, I was sitting watching TV when I suddenly decided I needed to get something out of my car.  When I went to get it, I found that a young male cardinal had got into my car through a window that was open about two inches and couldn't get out.  He was now sitting on the floor and breathing with difficulty.  If I hadn't found him and let him out when I did, he would have died from the heat.  I'm still not exactly sure what the message was of that encounter.  To see a cardinal often symbolizes poor nutrition and is a warning to eat better.  It can also symbolize the need to balance material needs with your spiritual goals.