From barnyard to backyard, lowly hens have flown the country coop and joined the city chicken movement. A new generation of small-acreage farmers raising heritage breeds has inspired urbanites and suburbanites across America to install some poultry out back for eggs, meat, fertilizer, and cockeyed companionship. Whether the breed is Jersey Giant, Wyandotte, Buff Orpington, or Silver Frizzle Polish--chickens are now chic.     This is not a how-to book on raising chickens but rather a wry, fascinating, sometimes startling appreciation of them, conveyed in compelling accounts by Susan Troller and striking prints and paintings by S.V. Medaris. A bonus: chicken stories from three of Wisconsin's most celebrated writers--Jane Hamilton (The Book of Ruth, A Map of the World), Michael Perry (Coop, Population 485), and Ben Logan (The Land Remembers)--round out the collection.