Color
Relying on the observation of the color of a bird's feathers as well as field marks, which are specific markings that each species of birds possesses, is among the most commonly used method of bird identification.
Silhouette
An important way to identify a bird is to look at its silhouette, make an estimate of the bird's size, take note of its shape and then decide which family of birds it belongs to by using references that will readily have such information available.
Geography
Where a bird is seen in terms of terrain--such as meadows, forests, urban areas or near water--can be a useful identification tool that the experienced bird watcher will employ.
Behavior
How a bird behaves as it is being observed can give the bird watcher many clues, with such behaviors as how the bird flies, perches, moves while on the ground and eats being important factors.
Sounds
Birds will sing and make frequent calls that can be used to positively identify them; audio tapes of bird calls and online sites that have recording of their songs are used for this purpose.
