Large- and Small-Scale Climate Influences Spring Migration Departure Probability of American White Pelicans

Abstract

Endogenous (e.g., age and sex) and exogenous (e.g., climate and resource availability) factors influence avian migration phenology. However, little is known regarding the migration ecology of birds at the non-breeding grounds, including the American white pelican (Pelecanus erythrorhynchos). We used Global Positioning System transmitters to track the movements and migration of 51 pelicans from 2002 to 2012. We used the Kaplan–Meier model to estimate pelican spring migration probabilities to quantify partial migration with 94 spring migration events and used the Cox proportional hazards model to evaluate the effects of the North Atlantic Oscillation index (NAOI), Southern Oscillation Index (SOI), and spring daily precipitation on the propensity of pelican spring migration departures. Increases in the NAOI and SOI enhanced the propensity of pelican spring departure. The propensity of spring departure was also positively related to daily precipitation. Male pelicans have greater spring migration probabilities than female pelicans. Spring migration departure probabilities of adult pelicans are greater than those of immature pelicans. Therefore, both large-scale and local climatic conditions affect pelican spring departure probabilities. Advanced migratory phenology of pelicans caused by climate changes with warming temperature and increased precipitation may result in the mismatch of pelican spring arrival with food resource availability of breeding grounds and subsequent pelican population declines.