This bird guide goes beyond IDs; A Guide to Bird Behavior, Volume II: In the Wild and At Your Feeder, by Donald W. Stokes and Lillian Q. Stokes. Illustrated by John Sill, Deborah Prince, and Donald Stokes. Boston, Toronto: Little, Brown & Company. 334 pp. $14.95.

For more and more people, the fun in the game of bird watching is in finding out what the birds do. It is no longer enough to find birds, identify them, and add them to one's life list.

So books are coming out which describe the behavior of commonly seen birds, or which aim to teach what to look for in order to get you started in the more rewarding aspects of bird watching.

One especially rewarding aspect is that there is still room for the competent amateur to contribute his observations to the gradually accumulating body of scientific knowledge. Only a few birds, such as pigeons, have been studied intensively.

Donald and Lillian Stokes have written a series of nature guides designed to promote understanding of the world around us. The first volume in their series ''A Guide to Bird Behavior'' was such a success that they have added a second, including 25 more birds of backyard and countryside varieties.

''Birds are always presenting us with a wealth of information about their lives; however, most of this exciting information goes unnoticed,'' they begin. ''The difference between receiving or missing it is only a matter of a few minutes of observation, some curiosity, and a little information.'' You provide the observation and curiosity; the authors give you the information necessary to get started.

They also provide a caveat: ''What a bird does and why it does it are two different things. One is based on observation and is therefore mostly fact; the other is based on assumption and therefore is mostly speculation.'' It is tempting to attribute human characteristics and motives to the birds, they warn. Careful observation may lead one to find out the birds' reasons for doing what they do.

To this end, the Stokeses offer a number of guidelines to consider while observing. The chapter on each bird is organized into introduction, behavior calendar, display guide (both visual and auditory), and descriptions of varieties of behavior.

The helpful black and white drawings illustrate bird postures and nests. The verbal descriptions of bird sounds, however useful, still don't solve the very difficult problem of how to convey what one hears. The best way remains to listen.