Food provisioning in Magellanic penguins as inferred from stable isotope ratios

Ciancio, Javier; Yorio, Pablo; Wilson, Rory P.; Frere, Esteban

doi:10.1002/rcm.8065

Cited by 8 publications

(10 citation statements)

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“…Because this difference is driven by the δ 13 C, it is most likely that both sexes prey on similar trophic level prey in different areas in the sea. Additionally, stable isotope signatures were similar to penguin breeding in northern colonies during chick rearing (Ciancio et al ), which agrees with the main northward migration shown by GLS tags. As expected, sexes showed similar isotopic niches later in the season during chick rearing while they behave as central place foragers and showed similar stable isotope values compared to other predators in the region (Ciancio et al ).…”

Section: Discussionsupporting

confidence: 83%

Geolocation and stable isotopes indicate habitat segregation between sexes in Magellanic penguins during the winter dispersion

Barrionuevo

Ciancio

Steinfurth

et al. 2020

Journal of Avian Biology

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The Magellanic penguin Spheniscus magellanicus is a top predator and a major consumer of marine resources in the Patagonian Continental Shelf and worldwide. It is the most migratory of the Spheniscus penguins, but until recently, its migration route was only partially known. Our aims with regard to the Magellanic penguin breeding on Isla Quiroga, Argentina, were: 1) to compare the distribution during the winter period between sexes and 2) in case that habitat is segregated, to evaluate possible proximate causes like competitive exclusion and/or habitat specialization. In March 2017 and 2018, prior to migration, we equipped 26 penguins with MK3/4 geolocators, which were recovered in late September/early October. Penguins dispersed northwards up to 29°S and southwards up to 56°S, near the Beagle Channel, being distributed over 2158 ± 50 km of latitudinal range and showing a large‐scale distribution pattern across longitudes in waters within the continental shelf. We found a longitudinal segregation between sexes in their winter grounds, with males closer to the 200‐m isobath and further from the coastline than females. Morphological and physiological differences between sexes might allow males to dive deeper at a lower cost than females, which could result in a more offshore path for males. This spatial segregation was supported by bulk blood stable isotope values and estimated isotopic niche, which differed between males and females at their arrival from winter breeding grounds, but not while penguin breed and behave as central place foragers in the colony. For the first time in this species, we combined two independent tools, geolocation and stable isotope data, and find that sexual segregation in habitat use could potentially generate an optimal winter foraging strategy for both sexes, precluding potential intersex competition for food.

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Section: Discussionsupporting

confidence: 83%

Geolocation and stable isotopes indicate habitat segregation between sexes in Magellanic penguins during the winter dispersion

Barrionuevo

Ciancio

Steinfurth

et al. 2020

Journal of Avian Biology

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“…, Ciancio et al. ). Evidence from non‐breeding areas suggests that female Magellanic Penguins are more susceptible to starvation.…”

Section: Discussionmentioning

confidence: 97%

“…For example, recent studies suggest that males provision more food to Magellanic Penguin chicks than do females (Ciancio et al. ), despite similar duration foraging trips during the breeding season.…”

Section: Discussionmentioning

confidence: 99%

“…On average, adult male Magellanic Penguins are 17% heavier than adult females and have bills that are 8% longer and 15% deeper (Boersma et al 2013). Relative to males, female Magellanic Penguins may experience (1) shallower or less frequent diving due to a lower oxygen storage capacity (Walker and Boersma 2003), (2) higher drag due to a greater surface area to volume ratio, (3) less resilience to periods of food scarcity due to a lower food storage capacity (Colchero et al 2017), and (4) less prey size flexibility due to smaller bills (e.g., Vanstreels et al 2013, Silva et al 2014, Ciancio et al 2018. Evidence from non-breeding areas suggests that female Magellanic Penguins are more susceptible to starvation.…”

Section: Intraspecific Variation In Foraging and Survivalmentioning

confidence: 99%

“…Even if females and males have similar diets, females may have to work harder to maintain body condition. For example, recent studies suggest that males provision more food to Magellanic Penguin chicks than do females (Ciancio et al 2018), despite similar duration foraging trips during the breeding season.…”

Section: Intraspecific Variation In Foraging and Survivalmentioning

confidence: 99%

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Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Gownaris

Boersma

2019

Ecological Applications

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We developed a Hidden Markov mark–recapture model (R package marked) to examine sex‐specific demography in Magellanic Penguins (Spheniscus magellanicus). Our model was based on 33 yr of resightings at Punta Tombo, Argentina, where we banded ~44,000 chicks from 1983 to 2010. Because we sexed only 57% of individuals over their lifetime, we treated sex as an uncertain state in our model. Our goals were to provide insight into the population dynamics of this declining colony, to inform conservation of this species, and to highlight the importance of considering sex‐specific vital rates in demographic seabird studies. Like many other seabirds, Magellanic Penguins are long‐lived, serially monogamous, and exhibit obligate biparental care. We found that the non‐breeding‐season survival of females was lower than that of males and that the magnitude of this bias was highest for juveniles. Biases in survival accumulated as cohorts aged, leading to increasingly skewed sex ratios. The survival bias was greatest in years when overall survival was low, that is, females fared disproportionality worse when conditions were unfavorable. Our model‐estimated survival patterns are consistent with independent data on carcasses from the species’ non‐breeding grounds, showing that mortality is higher for juveniles than for adults and higher for females than for males. Juveniles may be less efficient foragers than adults are and, because of their smaller size, females may show less resilience to food scarcity than males. We used perturbation analysis of a population matrix model to determine the impact of sex‐biased survival on adult sex ratio and population growth rate at Punta Tombo. We found that adult sex ratio and population growth rate have the greatest proportional response, that is, elasticity, to female pre‐breeder and adult survival. Sex bias in juvenile survival (i.e., lower survival of females) made the greatest contribution to population declines from 1990 to 2009. Because starvation is a leading cause of morality in juveniles and adults, precautionary fisheries and spatial management in the region could help to slow population decline. Our data add to growing evidence that knowledge of sex‐specific demography and sex ratios are necessary for accurate assessment of seabird population trends.

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Parental body condition and high energy value of fish determine nestling success in Magellanic penguin (Spheniscus magellanicus)

et al. 2018

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Food provisioning in Magellanic penguins as inferred from stable isotope ratios

Cited by 8 publications

References 58 publications

Geolocation and stable isotopes indicate habitat segregation between sexes in Magellanic penguins during the winter dispersion

Geolocation and stable isotopes indicate habitat segregation between sexes in Magellanic penguins during the winter dispersion

Sex‐biased survival contributes to population decline in a long‐lived seabird, the Magellanic Penguin

Parental body condition and high energy value of fish determine nestling success in Magellanic penguin (Spheniscus magellanicus)

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