How do certain species of birds such as humming birds, terns, gulls and kestrels remain in the air without a forward

Question: How do certain species of birds such as humming birds, terns, gulls and kestrels remain in the air without a forward motion?
- Keywords:
  bird,
  flight,
  flying,
  hovering,
  motion
Asked by alysha to Hitesh, Hywel, Mae, Nik, Tiffany on 13 Jun 2012.
- Tiffany Taylor answered on 13 Jun 2012:
  
  By moving their wings in a special way they can create lift (which keeps them in the air) without forward motion. I know there’s more to it but I don’t know much more about it than that!
- Hitesh Dave answered on 21 Jun 2012:
  
  I think their body create balance between their wings and trunk…like Aerodynamics position…and because of it they can be lifted in the air without even a froward motion…

Question: How do certain species of birds such as humming birds, terns, gulls and kestrels remain in the air without a forward motion?