There are many ways to identify bird species, and one of the easiest places to start is posture. Birds that I am familiar with typically have either an erect (vertical) posture, or a horizontal posture. Noting the kind of posture that a bird has is often the first step of the identification process when I see a bird that I don't instantly recognize. While the bird pictured below is one that I am extremely familiar with, I can quickly run through the process I would have used when learning it.

Carolina Wren

The Carolina Wren is an excellent example of a bird whose posture is typically horizontal, and when such posture is observed alongside a cocked tail and distinctive field marks (characteristics used to I.D. individual species) such as the white stripe above the eye; brown-colored back and wings; and clear, lightly colored breast, then there's not any other bird in my area that it could possibly be. This particular wren is facing a wall in which it has built a nest (its second one this season), and has flown in to check me out. I was sitting on a bench perhaps 12 feet away.

These birds are extremely inquisitive, and I've noticed they will go out of their way to inspect whatever catches their attention. If that attention-grabber happens to be an intruder, they will make a "scolding" noise and attack it with extreme prejudice. They will attack snakes, cats, dogs, squirrels, other birds, and people alike. Other species that share their habitat with Carolina Wrens will, in the interest of protecting their own nest sites from the wren's target, often react to scolding. As a result, birders can imitate the call (this is known as "pishing") to attract birds that are hidden in trees or brush. All in all, the Carolina Wren is a bird with personality, and a personal favorite of mine.