California's brown pelicans, nearly driven to extinction by poisons a half century ago, are in trouble again, and no one knows why. The problem may be a sign that a long-expected El NiÃ±o event is heading across the Pacific earlier than expected, but that's only a possible explanation, said Anderson, who has counted the pelican pairs breeding on the islands in Mexico's Gulf of California every year for the past 46 years. El NiÃ±o years occur irregularly, but when they do, ocean circulation warms in the Eastern Pacific, bringing heavier rains than usual to the western Americas, and makes fishing poor for pelicans and other seabirds. The pelicans arrived at their nesting grounds a good six weeks earlier than usual this year, a possible early sign of another El NiÃ±o event, Anderson said, but there's no certainty. The California brown pelican, Pelicanus occidentalis californicanus, has long been an iconic bird, but in the 1960s biologist Robert Risebrough of UC Berkeley began noticing widespread pelican deaths on California's Channel Islands.