Abstract

SECO PON, Juan Pablo  and  GARCIA, Germán Oscar. MAGELLANIC PENGUIN (SPHENISCUSMAGELLANICUS) IN THE NORTHERN ARGENTINEAN COAST: EVIDENCE OF SEXUAL BIAS IN STRANDED JUVENILE BIRDS?. Hornero [online]. 2022, vol.37, n.1, pp.6-6. ISSN 0073-3407.

The Magellanic Penguin (Spheniscus magellanicus) breeds off the southern coasts of South America, with colonies in Chile and Argentina, including the Malvinas Islands. The species exhibits seasonal migration during winter, reaching the coasts of the province of Buenos Aires in Argentina, and also in Uruguay and southern Brazil. In Argentina, and during that season, aspects re-lated to this species’ ecology and the implications for conservation biology remain enigmatic. In this study, we examined the occurrence of an asymmetric sex ratio among juvenile penguins stranded on the northern coast of Argentina. In total, 187 individuals were analyzed (approximately 46.5% of the total number of birds, n = 402) whose sex was determined by direct observation of their gonads throughout the study period (summer seasons of 2017, 2018, 2019 and 2021). Our findings suggest an asymmetric sex ratio, with 64% female individuals, representing 1.83 stranded females for each male. On the other hand, our research shows that the juvenile individuals stranded on southeastern Buenos Aires present differences in their biometric measurements between sexes (at least in head length and wing length). The present study is the first to use stranded birds to analyze the sex ratio in the Magellanic Penguin during the non-breeding season in Argentina.

Keywords : Argentina; Magellanic Penguin; migration; Province of Buenos Aires; sea birds; strandings.

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