THE HERONS OF THE WORLD, by James Hancock and Hugh Elliott. Paintings by Robert Gillmor and Peter Hayman. Foreword by Roger Tory Peterson (Harper & Row, $65). This is an elegant, oversize volume, recording and celebrating with scholarship and art the world's herons. Undoubtedly it will become a collector's item, says Roger Tory Peterson in his foreword, "... not one that will stay for long on the bookshelf. It will be referred to often." Indeed these large and graceful, long-legged wading birds -- ancient, resilient, adaptable -- have a spellbinding quality, attracting amateur and professional bird people. Herons seem to bless by their presence Indian rice paddies, heronries in England, in Japan, and -- for Washington's canoeists and hikers -- the shores of the Potomac. The authors, whose travels and credentials are formidable, have seen three-quarters of the 61 species in the book. For about 20 they had too much material to summarize easily. For others, gaps remain. For two experts, they write unpretentiously. When it's "rather scrappy observation" or conjecture, they say so. Attempting to convey character as well as appearance, they describe the birds, drawing upon an extensive study of the literature, from field acquaintance, and by drawing on findings from new technical developments in radio tracking, sound recording, nocturnal observation. For each species, there is information on its range, movements, habitat, identification, and behavior. Observations range over the nestbuilding practices of the Paddybird; the Black Heron's canopy stance which causes it to resembles a peripatetic umbrella; the resurgence of the Snowy Egret, once all but done in by plume hunters. There are extensive references and splendid full-page color plates (61, to be exact) of paintings by two distinguished artists, in the Audubon tradition.