Within- and among-colony variation in non-breeding dispersion of Magellanic penguins breeding along the coast of Argentina

Abstract

Magellanic penguins Spheniscus magellanicus are upper trophic level predators and play a key role within their marine ecosystems. However, we lack detailed understanding of their non-breeding distribution where they might be impacted by human threats and climate change. Using geolocator tracking devices deployed in 2021, we analyzed individual non-breeding movements, and differences in the spatial, environmental, and trophic niches of Magellanic penguins breeding along the Atlantic coast of Argentina. The results show that movement characteristics, including trip lengths and dispersal distance, were similar among individuals and across colonies. However, the temporal pattern, including the timing of arrival to the breeding sites, differed between colonies. During the non-breeding season, distributions showed considerable overlap between colonies, notably between individuals from the central and the northernmost breeding sites. Individuals from the northern and central colonies faced similar oceanographic features (i.e. sea surface temperature, chlorophyll a, salinity, depth) and used similar foraging niches while within the anchovy geographic domain. In contrast, individuals breeding farther south were feeding within the geographically distinct sprat domain. Our results indicate that Magellanic penguins breeding along the latitudinal range of Argentina express a broad variation in habitat use during the non-breeding period, and make use of a large proportion of the Patagonian Shelf. The latitudinal location of the breeding colony seems to define the trophic niche and where individuals move during the non-breeding season.