The first thing that registers in the mind upon seeing a bird is the combination of size and color. As a frame of reference, consider three birds common to virtually everyone: a sparrow, robin, and crow. When a bird pops into view, you might say, “It’s a gray robin-size bird” or “The bird I saw was about sparrow-size and blue.”
Once you have determined the general color and size, try to pick up any distinguishing features such as colored bars on the wings, a cap on the head, or a ring around each eye. Hopefully, if the bird stays in view long enough, you will have time to build a mental picture of the bird with enough field marks, as they are called, to make identification simpler.
Consider the “gray robin-size bird.” You’ve already eliminated many birds such as sparrows, finches, and warblers by judging its size. Now look for other distinguishing features. You may see a black cap and a rusty-colored patch under the tail, two more identifying marks. Listen for its song or call note. You may hear a distinctive catlike “mew.” Also note its habitat. Is the bird found in brushy areas or along a wooded edge? Keep these all in mind, or better yet, record what you see and hear in a notebook.
Favorite field guides
Kaufman Field Guide to Birds of North America by Kenn Kaufman
The Sibley Guide to Birds by David Allen Sibley
The Crossley ID Guide: Eastern Birds by Richard Crossley
Peterson Field Guide to Birds of North America by Roger Tory Peterson
National Geographic Field Guide to the Birds of North America, Sixth Edition by Jon L. Dunn and Jonathan Alderfer
The Stokes Field Guide to the Birds of North America by Donald and Lillian Stokes
The Young Birder’s Guide to Birds of Eastern North America by Bill Thompson III
Birds of Eastern North America: A Photographic Guide by Paul Sterry and Brian E. Small
Birds of Western North America: A Photographic Guide by Paul Sterry and Brian E. Small
Once you have a set of field marks in mind or jotted down, consult a field guide. Several excellent field guides are listed here. Most birders carry one with them into the field. A large vest pocket or fanny pack will hold your guide for quick reference.
The gray bird with the catlike sound? Paging through the songbird section in a field guide will reveal the Gray Catbird.