Three very similar species of small, gray and white alcids (Synthliboramphus) occur in southern California and in northwestern Mexico. Guadalupe Murrelet has the most distinctive appearance of these three; it also is the rarest, most geographically restricted, and least known member of the group. Guadalupe Murrelet is known to breed on Guadalupe and San Benito islands, off the Pacific coast of Baja California; after breeding, it disperses north to waters off of central California. The natural history of Guadalupe Murrelet otherwise is poorly documented, but presumably is similar to that of Scripps's Murrelet (Synthliboramphus scrippsi) and Craveri's Murrelet (Synthiloboramphus craveri). Guadalupe Murrelet is distinguished from both of these species by the greater extent of white on the sides of the face, especially the broad white crescent around the eye. Until recently, Guadalupe and Scripps's murrelets were classified as a single species, "Xantus's Murrelet", but they now are recognized as a separate species, as they are locally sympatric as breeders on San Benito Island, differ in face pattern and in bill shape, and have different vocalizations. Guadalupe Murrelet is classified as Endangered, based on its small breeding range and global population, and because its population is believed to be decreasing.