For a shortcut to trails in your region, click the brief description below. WESTWARD HO! The astonishing diversity of birdlife in the West mirrors the extreme variety of conditions. SOUTHERN COMFORT: Throughout the South, birds are found in dazzling abundance. EASTERN EDENS: The Northeast Corridor may be the most heavily settled part of the country, but it is still a land of amazing natural riches. STOPOVER COUNTRY: Incongruous as it might seem, the center of the continent funnels millions of migrating birds. WESTWARD HO! When I trekked among the stark cactus gardens of the Arizona borderlands for the first time, I saw a dozen new birds for my life list in the first half-hour: quirky roadrunners, noisy cactus wrens, sleek phainopeplas, and enough others to make my head spin. The same thing happened when I hit central California’s rockbound coast, with its tattlers and surfbirds clambering over the boulders, gulls and terns swarming offshore. In the...