CAUSES OF NEST DESERTION DURING INCUBATION IN THE MAGELLANIC PENGUIN (SPHENISCUS-MAGELLANICUS)

We quantified the causes and rate of nest desertions in Magellanic Pen guins (Spheniscus magellanicus) during the egg stage at Punta Tombo, A rgentina. Incubating Magellanic Penguins rarely deserted. The average desertion rate during seven years was 11% (SD = 9.2%). Desertions were poorly correlated with the length of the incubation spell and only 25 % of the desertion could be accounted for by delayed nest relief. Body condition at the start of the incubation spell appears to be the most important factor in determining desertions. Penguins that deserted we re lighter for their body size at the time of egg laying than penguins that did not desert. Desertion was significant and common during the first part of incubation, the time when females are present. Flooded n ests were more likely to be deserted than nonflooded nests, but desert ions from flooding were few. High temperatures did not increase desert ion during incubation, thus it is unlikely that heat stress is an impo rtant cause of nest desertion. An individual's body condition appears to be the most important factor in explaining desertion but behavior o f the mate and other factors can play a role.