Bird word

Photoperiodism: The effect of light as determined by the length of the day on bird migration and nesting. Lengthening daylight, for example, stimulates the reproductive systems of many bird species, including our nesters.

Name that hawk See that large hawklike bird on the power post along the freeway as you drive the metro area? It's probably a red-tailed hawk. These birds normally hunt small mammals in open fields, but freeway edges work just as well. Milder winters have made it easier for red-tailed hawks to set migration aside.

Book in brief Many bird identification books read as though they were written by the terse cop Joe Friday, hero of the old TV series "Dragnet."

Not this one. "The Young Birder's Guide to Birds of Eastern North America" (Houghton Mifflin, $14.95) reflects the personality of its author, the jovial, banjo-playing, world-class storyteller and birder, Bill Thompson III. Don't be misled by the title. While it's a perfectly wonderful book for young birders, almost anyone who can use identification help now and then will enjoy it.

Thompson does a fine job on all the requisites: definitions, tips, lists, how-to information including "green" birding and an explanation of why birding no longer need be considered a nerd activity.

But what I love about this book is the delightful prose he uses to describe the field characteristics of the 200 bird species covered. For instance, the male gadwall ducks wear "black underpants," according to the author. (The female, he says, lacks such a garment.)

I doubt if anyone before has used such memorable language. I won't forget them. You won't either.

JIM WILLIAMS