The Private Life of Birds by Michael Bright Bantam $340 DIP into this book and you will quickly learn that while many birds go clandestinely about their business, others are extrovert. Nor are birds the goody two-shoes types you might expect from the limp ''feathered friends'' label sometimes foisted on them. Here, BBC Natural History Unit producer Michael Bright tells of birds that live as pirates, gangsters and vampires. Some male birds are preening, philandering dandies; others are weedy sex slaves. Birds can even verge on the downright bawdy: one species copulates to scare off the neighbours. Mr Bright starts his foray into the bird world with a brief account of the evolution of birds from small dinosaurs. He describes features such as feathers and wings and the refinements that have helped make birds such as the peregrine so masterful in theair. But the bulk of the book concerns the strategies which birds have developed for survival and to pass on their genes. Mr Bright has culled his material from many sources - the book is billed as ''a worldwide exploration of bird behaviour'' - but you do not have to travel, or even be a zealous bird-watcher, to see some of the strategies described. On finding food scattered across an area where predators may lurk, a sparrow calls to attract more birds so it can feed in the safety of a group. If it discovers just one piece of food in a safe place, it craftily sets about eating without even a ''cheep''. Birds also call to sound the alarm. One high, thin call given by songbirds can be annoyingly hard to locate; but that's the idea, the caller wants to remain unseen, and safe. Songs are more complex and can take weeks to learn. Though often beautiful to our ears, they too serve a purpose, telling rival males to keep away while hopefully enticing females. Males may also attract mates by showing off their extravagant plumage. Bowerbirds, by contrast, collect coloured leaves, flowers and other paraphernalia. A researcher watched as one bird attempting to woo a female revealed his prized possession - a tin mug. Birds' dietary tastes are diverse. Most vegetarian birds eat nutritious seeds or fruit. But not the hoatzin, an ancient bird that munches on leaves and has a digestive system like a cow. Other birds eat meat, or fish. A Galapagos finch pecks at nesting seabirds and sips their blood. In response to the changing seasons, millions of birds migrate, performing great feats of navigation as they follow routes that crisscross the globe. Spending summer in the far north, winter in the waters around Antarctica, the Arctic tern experiences more daylight than any other living creature. The book abounds with such ''Did you know?'' material. Reading it, however, I gained the impression that Mr Bright is not a bird-watcher as the birds are rarely brought to life. Nor does he display flair as a writer. Indeed, it often seems the book was written on ''cruise control''. But the information is interesting and sensibly presented and it helps to show why many find bird-watching rewarding: they are so entertaining. It may also boost arguments for conservation. For it shows that without birds the world would be immeasurably poorer.