Covering the thirty-six species of gulls that occur in North and South America, this unparalleled resource includes detailed identification information for the many plumages gulls display as they mature. More than just a field guide, this large and ambitious volume is the definitive reference work on gulls of the Americas. A group of birds that is popular among birdwatchers, gulls can be frustrating to identify, as they can take up to four years to mature, with different plumages each year. With 1,160 photographs illustrating these plumages, and descriptions by two of North America' s top gull experts, this new reference guide is the authoritative word on gulls.