The Hummingbird is, and has been, a spiritual symbol in many religions and beliefs, though usually not a major one.  It's significance is mostly based on the way it flies and eats.
    The hummingbird can fly forward, backwards, sideways and hover.  They are the only birds that can do that.  For this reasons, they sometimes symbolize mastery over time and, since mastery over time means spiritual development, they also symbolize spiritual development.  In Central and South America, the hummingbird is considered by many to have supernatural powers and is considered a love charm.   It is also considered a joyful bird so symbolizes joy, happiness.  
    The hummingbird is also noted for the fact that they will become very still, appearing to be dead, on cold nights, than wake up when the morning sun warms them.  For this reason, they also symbolize rebirth and immortality.
    According to the Taino people, the hummingbird symbolizes the spreading of life over the earth.  They also call their warriors Hummingbird Warriors because the hummingbird is peaceful, but will protect it's home.  
    Exactly what it symbolized to the people who made the Nazca Lines is unknown, but it is a very prominent figure in those lines.