LIVING ON THE WIND

A tidy and, for all its depth, nimble summation of current thinking on bird migration and attendant environmental themes from Weidensaul (Mountains of the Heart: A Natural History of the Appalachians, not reviewed). It is estimated that five billion birds take to the air on annual migrations. Most fly, many making those epic flights from the Arctic to South America. A few comedians, like the blue grouse, prefer to walk to their wintering venues and then back to their summerhouses come the spring. Weidensaul makes it clear from the outset that migration is a process of many parts—each bird, after all, has its own agenda—and he serves forth what is both known and conjectured. The book is broken up into three parts: the southern migration from North America in the autumn, an intermezzo that chronicles Weidensaul’s Latin American travels during the migrants’ wintering, and the return voyage north. Weidensaul ably blends specific behavioral material on individual species, atmospheric place notes as he traipses about following the birds, and theories concerning the hows and whys of migration, including navigation, the search for food, photoperiod triggers (though why he avoids discussion of chronobiology and circadian rhythms is a mystery), irruptions, and fallouts. His writing is full of affection for his subject—about the elbow room needed by cerulean warblers, for instance—and his description of the tens of thousands of hawks he witnessed in a churning, updrafting kettle is astonishing, but he can also crank out a painfully empurpled item on occasion: birds on “wings as fragile as a whisper,” or “aloft in the night air, migrant songbirds have the freedom of angels.” Environmental considerations pepper the book, in particular the role of habitat loss and fragmentation on migratory success that requires ample food, safe havens, and quiet roosts, clean water, and a destination left untampered. Intelligent and broadly inquisitive, Weidensaul provides the kind of revelatory anecdote that allows lay birders (and any other reader) to ratchet their appreciation of the avian world up a significant notch. (maps)