Determining the Nest Type

• Some bird species build nests on the ground, so it's best not to displace those nests.Photos.com/Photos.com/Getty Images
  
  Determining whether the nest truly fell out of the tree is important. Many bird species build their nests in places other than trees. Mallard ducks, for example, build mound nests on the ground near lakes, in yards or even near busy streets. Burrowing Owls will dig burrows in which they lay their eggs. If the nest you find belongs to a bird species that does not build its nests in trees, leaving the nest alone is best. You can determine the nest type by researching the kind of nest you found and the bird species that inhabit your area.
  
  

Determining the Nest's Occupancy

• Just because a nest is empty does not mean that it's been abandoned. The birds might return later.Anup Shah/Digital Vision/Getty Images
  
  Before moving an empty nest, check the area to verify that the birds have truly abandoned it. Often, fledglings, or young birds, have left the nest to practice flying and searching for food. In other cases, nestlings, or baby birds, have accidentally fallen out of the nest. If you find that a nestling has fallen out of the nest, replacing the bird in the nest is OK. It is a myth that bird parents will abandon their young if they sense that the young have been touched by humans. If you find an injured bird nearby, call your local Audubon Society, or SPCA. Each could help you determine what you can do for the young bird.
  
  

Replacing a Nest

• Setting an empty nest back in a tree is fine, as long as you consider a few factors.Thomas Northcut/Photodisc/Getty Images
  
  If you find a truly abandoned bird nest that has been knocked out of a tree, set it back in the tree from which it came, or in a nearby tree. If the nest is intact, put the nest in a fork in the tree's branches. Don't set the nest in direct sunlight. Don't try to reattach the nest using wire, as it can harm birds or tear feathers. Wash your hands after handling nests, as they often carry parasites such as mites or lice.
  
  

Cleaning a Found Nest

• Old nests or nests that are not intact could contain parasites, which can harm both adult and baby birds.Stockbyte/Stockbyte/Getty Images
  
  In some cases, replacing a nest is inadvisable. If a nest is not intact, it's best for birds to rebuild their nest. The primary reason for this is to reduce parasites such as mites or lice, which can cause health issues in birds. In cases where you find an empty, but intact, nest that looks as though it has been inhabited for awhile--evidence of bird droppings, feathers, and old debris--it's best that you discard the nest. These nests are not sanitary for you or the birds.