text: In conclusion, three factors seem to be playing a role in the range changes of nesting Elegant Terns. (i) The success of conservation measures in the terns nesting grounds both in Mexico and California has allowed an increased population growth of the species, and the exponential increase in the Isla Rasa colony in particular seems to be pushing reproductive pairs onto new nesting grounds in California. (ii) Superimposed on this systematic and continuous expansion, there is a pulse-like variation in local SST conditions in the Midriff, which seems to drive nesting pairs to emigrate toward California when surface seawater in the Midriff is too warm , the thermocline is too deep, and fish availability is poor. (iii) The decision by seabirds to abandon their traditional nesting grounds in the Midriff is compounded by the fishing effort during the previous season, which further increases the proportion of Elegant Terns migrating away from the Gulf of California.