Every family is a world: offspring provisioning and individual trophicniche consistencies in Magellanic penguins

DODINO SAMANTA; RICCIALDELLI, LUCIANA; POLITO, MICHAEL J.; RAYA REY ANDREA

Virtual

Congreso; 3rd World Seabird Conference; 2021

Breeding seabirds must balance foraging for themselves and feeding their chicks with the constraints imposed as central place foragers. We evaluated Magellanic penguin (Spheniscus magellanicus) adult and chick diets during the early and late chick rearing periods and assessed adult trophic consistency throughout the season for using carbon (13C) and nitrogen (15N) stable isotope values. We sampled blood cells (integrates information over months) and plasma (integrates information over weeks) from 13 families (adults and offspring) at Martillo Island colony during early-chick rearing (ECR) and late-chick rearing (LCR) periods in 2016. Isotopic niche width was larger during ECR than LRC for both tissues in chicks and adults. From ECR to LCR we found a significant decrease in plasma13C values of chicks and adults (C=0.5; 1.0? respectively) and blood cell 13C values for chicks only (C=0.8?). We also found a small decrease in plasma15N values for chicks and females (N=0.4?) and blood cell 15N values for females only (N=0.5?), without any changes in males. Despite these statistical differences, we estimated similar trophic position (TPs) between ages and stages (TPs≈3). Within-family variability accounted for 90% of the total isotopic variability and we did not find any differential food provisioning during ECR or LCR in both tissues (Euclidean distance analysis). By comparing tissues with differing turnover rates we found slightly higher individual niche consistency in males relative to females. In conclusion, we found no evidence of differential provisioning by parents, which contrasts with studies in northern Patagonia were chicks had diets most similar to males during LCR. Differences observed in isotopic niches could be due to a differential dietary evenness over time and/or different areas used, but with the consumption of prey occupying same trophic level, since penguins showed consistency in their TPs across the season.