Migratory variation in Magellanic Penguins

Submitted by Michi on 11 January 2024.

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Text by Melina Barrionuevo and photos by the Seabird Study Group of Austral Patagonia

The Magellanic penguin Spheniscus magellanicus, has always been considered to be one of the penguins that makes the longest annual migrations, with individuals previously found to travel over a thousand kilometres away from breeding areas during the non-breeding period. In our study, we tracked 14 individual Magellanic penguins from a colony near the southern part of their range with geolocating trackers. The colony was located at Cabo Vírgenes (52°21´S, 68°23´W), near the southern tip of Argentina.

​ Magellanic penguin.

The birds were fitted with geolocators between January and March whilst still in the area of the breeding colony and the devices were recovered between October and November of the same year when the birds returned for the next breeding season.

Once the geolocators were recovered, we analysed the data from May to August, which represents the area in which the birds were overwintering. We discovered a novel behavior in this species, which involves partial migration within the same colony. While 43% of the penguins remained within ~290 km of the breeding colonies, the others migrated as far as 2000 km to the north of the breeding colony – to the area of the Río de la Plata Estuary.

 Weighing a penguin.

The variability in the oceanic environment experienced by individuals in this colony depended on their behavior. Residents experienced colder and lower chlorophyll-a concentrations than migrants. This study reveals a novel behavior in one of the most migratory Spheniscus species and highlights the variability and adaptability of this species.

Whilst the number of birds that we tracked was relatively low, our study demonstrates that within a single population there is interesting variation in the over-wintering strategy of the penguins. Our data also suggested that there may be a gender-bias in long-distance migration, with most of the birds staying relatively close to the breeding area being female. Further research is needed to understand the causes and consequences of partial migration, particularly given the challenging climatic and oceanic conditions that are predicted for the future.