Warming oceanographic conditions, fishing pressure are driving nesting seabirds away from their ancestral breeding ground in Mexico into California harbors
Date:June 27, 2015
Source:University of California - Riverside
Summary:Warming oceanographic conditions and fishing pressure are driving nesting seabirds away from their ancestral breeding ground in Mexico into California harbors, a group of researchers has found.
Isla Rasa, in the Gulf of California, is renowned for its massive aggregations of nesting seabirds. Over 95 percent of the world populations of Elegant Terns and Heerman's Gulls concentrate unfailingly every year on this tiny island to nest. Ever since the phenomenon was described by L. W. Walker in 1953 the island has been a magnet for tourists, naturalists, filmmakers, and seabird researchers.
During some years in the last two decades, however, the seabirds have arrived to the island in April, as they usually do, but leave soon after without nesting. The first event was the 1998 "El Niño," when oceanic productivity collapsed all along the eastern Pacific coast from Chile to California. But then colony desertion happened again in 2003, and since then it has recurred with increasing frequency in 2009, 2010, 2014, and 2015. Researchers and conservationists were asking themselves where are the birds going when they leave their ancestral nesting ground, and what is causing the abandonment of their historic nesting site.