Tweet, tweet, you're dead

WAYNE GRADY

SILENCE OF THE SONGBIRDSHow We are Losingthe World's Songbirdsand What We Can Doto Save ThemBy Bridget StutchburyHarperCollins, 243 pages, $36.95About this time of the year, throughout the 1940s, weather radar operators would observe huge blips on their radar screens, large patches covering vast areas, sometimes whole states, that were not storms. They called these mysterious images "angels," and only later discovered that the angels were in fact enormous flocks of migrating songbirds, hundreds of millions of them, each individual bird reflecting a radar echo like a large drop of water. Today, Bridget Stutchbury writes, although there are still millions of migrants, "there is good reason to believe that the angels are slowly falling from the sky, dwindling in numbers year after year."