Harriers are a charismatic group of birds of prey with a worldwide distribution that have long fascinated bird watchers and scientists. Here for the first time the biology of the world's harriers is treated within one over, in readily accessible language. There are detailed comparisons of northern and southern species, descriptions of mating systems and population dynamics life histories, and insights into the selection pressures shaping the birds' life histories. The author addresses such questions as how females choose partners against their apparent self- interest, how they adjust to prevailing circumstances to produce the perfect clutch size, and what underlies variations in size dimorphism and copulation patterns. New information resulting from a DNA examination of the group reveals three new harrier species and allows construction of a new phylogeny of the harriers. The author's twin brother brings the book to life by fine original line drawings of these impressive birds. It will be a treat for all raptor biologists, amateur raptophiles, and behavioral ecologists interested in birds of prey.