Increasing environmental variability inhibits evolutionary rescue in a long-lived vertebrate.

Evolutionary rescue, whereby adaptive evolutionary change rescues populations from extinction, is theorized to enable imperiled animal populations to persist under increasing anthropogenic change. Despite a large body of evidence in theoretical and laboratory settings, the potential for evolutionary rescue to be a viable adaptation process for free-ranging animals remains unknown. Here, we leverage a 38-year dataset following the fates of 53,959 Magellanic penguins (Spheniscus magellanicus) to investigate whether a free-ranging vertebrate species can morphologically adapt to long-term environmental change sufficiently to promote population persistence. Despite strong selective pressures, we found that penguins did not adapt morphologically to long-term environmental changes, leading to projected population extirpation. Fluctuating selection benefited larger penguins in some environmental contexts, and smaller penguins in others, ultimately mitigating their ability to adapt under increasing environmental variability. Under future climate projections, we found that the species cannot be rescued by adaptation, suggesting similar constraints for other long-lived species. Such results reveal how fluctuating selection driven by environmental variability can inhibit adaptation under long-term environmental change. Our eco-evolutionary approach helps explain the lack of adaptation and evolutionary rescue in response to environmental change observed in many animal species.

Overlap between marine predators and proposed Marine Managed Areas on the Patagonian Shelf.

Static (fixed-boundary) protected areas are key ocean conservation strategies, and marine higher predator distribution data can play a leading role toward identifying areas for conservation action. The Falkland Islands are a globally significant site for colonial breeding marine higher predators (i.e., seabirds and pinnipeds). However, overlap between marine predators and Falkland Islands proposed Marine Managed Areas (MMAs) has not been quantified. Hence, to provide information required to make informed decisions regarding the implementation of proposed MMAs, our aims were to objectively assess how the proposed MMA network overlaps with contemporary estimates of marine predator distribution. We collated tracking data (1999-2019) and used a combination of kernel density estimation and model-based predictions of spatial usage to quantify overlap between colonial breeding marine predators and proposed Falkland Islands MMAs. We also identified potential IUCN Key Biodiversity Areas (pKBAs) using (1) kernel density based methods originally designed to identify Important Bird and Biodiversity Areas (IBAs) and (2) habitat preference models. The proposed inshore MMA, which extends three nautical miles from the Falkland Islands, overlapped extensively with areas used by colonial breeding marine predators. This reflects breeding colonies being distributed throughout the Falklands archipelago, and use being high adjacent to colonies due to central-place foraging constraints. Up to 45% of pKBAs identified via kernel density estimation were located within the proposed MMAs. In particular, the proposed Jason Islands Group MMA overlapped with pKBAs for three marine predator species, suggesting it is a KBA hot spot. However, tracking data coverage was incomplete, which biased pKBAs identified using kernel density methods, to colonies tracked. Moreover, delineation of pKBA boundaries were sensitive to the choice of smoothing parameter used in kernel density estimation. Delineation based on habitat model predictions for both sampled and unsampled colonies provided less biased estimates, and revealed 72% of the Falkland Islands Conservation Zone was likely a KBA. However, it may not be practical to consider such a large area for fixed-boundary management. In the context of wide-ranging marine predators, emerging approaches such as dynamic ocean management could complement static management frameworks such as MMAs, and provide protection at relevant spatiotemporal scales.

Genetic evidence of hybridization between Magellanic (Sphensicus magellanicus) and Humboldt (Spheniscus humboldti) penguins in the wild.

The process of hybridization between closely related species plays an important role in defining the genetic integrity and overall genetic diversity of species. The distribution range of Magellanic (Spheniscus magellanicus) and Humboldt (Spheniscus humboldti) penguins is predominantly allopatric; however, the species share a region of sympatry where they may hybridize. We analyzed four types of genetic markers (including nuclear and mitochondrial markers) to assess their utility in detecting hybridization events between Magellanic and Humboldt penguins. Genetic assessment of non-introgressed reference samples allowed us to identify three types of informative markers (microsatellites, major histocompatibility complex, and mitochondrial DNA) and detect positive evidence of introgressive hybridization in the wild. Four out of six putative hybrids showed positive evidence of hybridization, revealed by the detection of Humboldt mitochondrial DNA and Magellanic species-specific alleles from nuclear markers. Bayesian Structure analysis, including samples from the sympatric region of the species in the southern Pacific Ocean, confirmed the use of nuclear markers for detecting hybridization and genetic admixture of putative hybrids, but revealed relatively low levels of genetic introgression at the population level. These findings provide insights into the role of hybridization in regions of species sympatry and its potential consequences on the levels of genetic introgression, genetic diversity, and conservation of these penguin species.

Effects of El Niño and La Niña Southern Oscillation events on the adrenocortical responses to stress in birds of the Galapagos Islands.

El Niño Southern Oscillation events (ENSO) and the subsequent opposite weather patterns in the following months and years (La Niña) have major climatic impacts, especially on oceanic habitats, affecting breeding success of both land and sea birds. We assessed corticosterone concentrations from blood samples during standardized protocols of capture, handling and restraint to simulate acute stress from 12 species of Galapagos Island birds during the ENSO year of 1998 and a La Niña year of 1999. Plasma levels of corticosterone were measured in samples collected at capture (to represent non-stressed baseline) and subsequently up to 1 h post-capture to give maximum corticosterone following acute stress, and total amount of corticosterone that the individual was exposed to during the test period (integrated corticosterone). Seabird species that feed largely offshore conformed to the brood value hypothesis whereas inshore feeding species showed less significant changes. Land birds mostly revealed no differences in the adrenocortical responses to acute stress from year to year with the exception of two small species (<18 g) that had an increase in baseline and stress responses in the ENSO year - contrary to predictions. We suggest that a number of additional variables, including body size and breeding stage may have to be considered as explanations for why patterns in some species deviated from our predictions. Nevertheless, comparative studies like ours are important for improving our understanding of the hormonal and reproductive responses of vertebrates to large scale weather patterns and global climate change in general.

A fearful scourge to the penguin colonies: Southern giant petrel (Macronectes giganteus) predation on living Magellanic penguins (Spheniscus magellanicus) may be more common than assumed.

Southern giant petrels (Macronectes giganteus) are important consumers that range across the oceans throughout the southern hemisphere. In Argentina, previous studies have shown they eat primarily pinnipeds and penguins, which they are assumed to scavenge, although there are occasional anecdotes of them attacking living penguins. Here we describe a predation attempt by a trio of southern giant petrels on a molting adult Magellanic penguin (Spheniscus magellanicus) at the large colony at Punta Tombo, Argentina. We relate giant petrel attendance patterns at the colony to the penguins' phenology, showing how giant petrel numbers rise with the increasing prevalence of vulnerable penguins. We suggest that living penguins-both fledglings and adults-may constitute a more seasonally significant proportion of the giant petrel diet than previously assumed, and their capture may represent a specialized predation technique.

Foot darkening with age in Spheniscus penguins: applications and functions.

The proportions of individuals in various age classes in a population of wild animals affect population trends, behaviors, learning, and social structures. Knowledge of age structure is needed for effective conservation and management of populations. However, it is not always possible to determine the age or age class of individual animals, and hence the age structure of the population. Penguins, like most birds, cannot be aged once they molt into adult plumage. Spheniscus penguins attain adult plumage at 6 to 24 months of age, and individuals can live more than 30 years. We studied foot darkening in the four species of Spheniscus penguins to determine if age class can be determined from foot color. We compared how foot color changes with age among the four species to investigate potential functions of the darkening. We found that Spheniscus penguins have pale feet at hatching and the feet become darker with age throughout the lives of individuals. We showed that we can accurately predict the age structure of a colony of Magellanic penguins Spheniscus magellanicus, but not the ages of individual penguins, based on a sample of foot colors. The timing of foot darkening within species was consistent with foot color functioning in protection from UV radiation, and not with foot color functioning in thermoregulation. The species that breeds at the lowest latitudes and experiences the highest UV radiation (Galápagos penguins Spheniscus mendiculus) had feet that darkened at the earliest ages, and the species that breed at higher latitudes and experience less intense insolation (African S. demersus and Magellanic penguins) had feet that darkened latest. Humboldt penguins S. humboldti breed mostly at low latitudes and foot darkening was intermediate between Galápagos and Magellanic penguins. We also found that males' feet darken somewhat earlier than females' feet, likely because females spend more time in their nests (burrows or under vegetation) than males and have less sun exposure. We found that feet darkened in an individual over years, but not within a breeding season. The color change is a life-long process, likely an evolutionary adaptation within species, not a seasonal, temporary response to UV radiation. We propose foot darkening as a way to assess age structure in Spheniscus penguins. Foot color in a colony of Magellanic penguins can provide a rapid, noninvasive method to estimate the age structure of the colony.

Changing course: Relocating commercial tanker lanes significantly reduces threat of chronic oiling for a top marine predator.

A goal for conservation biologists is to show that policies enacted on behalf of an imperiled species results in direct benefits for it. In Argentina, tens of thousands of Magellanic penguins (Spheniscus magellanicus) were estimated to have died from chronic oil pollution each year through the early 1980s. From 1982 to 1990, surveys at sites along approximately 900 km of Chubut Province coastline found that >60 % of penguin carcasses had evidence of oiling in some years. In response to these findings, as well as pressure from non-governmental organizations and the public, provincial and federal authorities in Chubut moved the commercial tanker lanes 20 nautical miles farther offshore in 1997 and required oil tankers to have double hulls. During a second round of surveys in 2001, using most of the same sites as the first survey period, the number of dead and oiled penguins dropped effectively to zero. A policy change not only led to fewer oiled penguins, but also likely increased the survival of adult Magellanic penguins near some of their most significant breeding colonies in Argentina.

MHC diversity and mate choice in the magellanic penguin, Spheniscus magellanicus.

We estimated levels of diversity at the major histocompatibility complex (MHC) class II DRß1 gene in 50 breeding pairs of the Magellanic penguin and compared those to estimates from Humboldt and Galapagos penguins. We tested for positive selection and 2 conditions required for the evolution of MHC-based disassortative mating: 1) greater MHC diversity between breeding pairs compared to random mating, and 2) associations between MHC genotype and fitness. Cloning and sequencing of the DRß1 gene showed that Magellanic penguins had higher levels of genetic variation than Galapagos and Humboldt penguins. Sequence analysis revealed 45 alleles with 3.6% average proportion of nucleotide differences, nucleotide diversity of 0.030, and observed heterozygosity of 0.770. A gene phylogeny showed 9 allelic lineages with interspersed DRß1 sequences from Humboldt and Galapagos penguins, indicating ancestral polymorphisms. d (N)/d (S) ratios revealed evidence for positive selection. Analysis of breeding pairs showed no disassortative mating preferences. Significant MHC genotype/fitness associations in females suggest, however, that selection for pathogen resistance plays a more important role than mate choice in maintaining diversity at the MHC in the Magellanic penguin. The differential effect of MHC heterozygosity on fitness between the sexes is likely associated with the relative role of hatching and fledging rates as reliable indicators of overall fitness in males and females.

Occurrence of Magellanic penguins along the Northeast Brazilian coast during 2008 Austral winter.

During the austral winter of 2008, thousands of penguins traveled to low latitudes along the South Atlantic coast of South America. The atmospheric and oceanic conditions from April to July 2008 may account for the penguins' unusual geographic distribution. During that period, South Atlantic coastal waters were cooler; the wind anomalies had northward and onshore components; the ocean's coastal region presented northward currents that favored the penguins to travel toward lower latitudes. This anomalous climate regime resulted from extreme meteorological frontal systems that occurred mainly during June 2008. Three consecutive extreme midlatitude cyclones produced strong wind shear that resulted in the northward oceanic flow along the South American eastern shoreline favoring the penguins to be spotted in northern tropical waters.

Consequences of phenological shifts and a compressed breeding period in Magellanic penguins.

Phenological shifts may ameliorate negative effects of climate change or create carryover effects and mismatches that decrease fitness. Identifying how phenological shifts affect performance is critical for understanding how individuals and populations will respond to climate change, but requires long-term, longitudinal data. Using 34 yr of data from the Magellanic penguin (Spheniscus magellanicus) colony at Punta Tombo, Argentina, we examined the consequences of the delayed onset of breeding (i.e., arrival and egg-laying dates) that has occurred at the colony since 1983. To understand how the delay propagates through the rest of the reproductive cycle, we identified phenological trends in hatch and fledge dates. Median hatch dates were 0.29 d later each year, amounting to a 10-d shift over the course of the study. Median fledge dates did not shift over the 34-yr period, however, thus shortening the median nestling period duration by 14%. We tested several predictions regarding performance outcomes of the compressed nestling period, finding that later-hatched chicks fledged significantly younger than earlier-hatched chicks, and that younger fledglings left the colony with smaller bills and with more chick down. Interestingly, although younger chicks fledged significantly lighter and in worse body condition than older fledglings early in the study, this trend reversed over time, with younger chicks actually fledging heavier and in better body condition in more recent years. Smaller and lighter fledglings were less likely to recruit to the colony as adults. We find that delayed breeding has significantly compressed nestling periods at Punta Tombo, influencing chick growth and fledgling condition. These findings highlight the importance of studying phenology across multiple life events to understand the consequences of phenological shifts for organismal fitness.

Feet first: Adaptive growth in magellanic penguin chicks.

Growing animals should allocate their limited resources in ways that maximize survival. Seabird chicks must balance the growth of features and fat reserves needed to survive on land with those needed to successfully fledge and survive at sea. We used a large, 34-year dataset to examine energy allocation in Magellanic penguin chicks. Based on the temporal trends in the selective pressures that chicks faced, we developed predictions relating to the timing of skeletal feature growth (Prediction 1), variation in skeletal feature size and shape (Prediction 2), and responses to periods of high energetic constraint (Prediction 3). We tested our predictions using descriptive statistics, generalized additive models, and principal component analysis. Nearly all of our predictions were supported. Chicks grew their feet first, then their flippers. They continued to grow their bill after fledging (Prediction 1). Variance in feature size increased in young chicks but declined before fledging; this variance was largely driven by overall size rather than by shape (Prediction 2). Chicks that died grew slower and varied more in feature size than those that fledged (Prediction 2). Skeletal features grew rapidly prior to thermoregulation and feet and flippers were 90% grown prior to juvenile feather growth; both thermoregulation and feather growth are energetically expensive (Prediction 3). To avoid starvation, chicks prioritized storing mass during the first 10 days after hatching; then, the body condition of chicks began to decline (Prediction 3). In contrast to our prediction of mass prioritization in young chicks, chicks that were relatively light for their age had high skeletal size to mass ratios. Chicks did not show evidence of reaching physiological growth limits (Prediction 3). By examining energy allocation patterns at fine temporal scales and in the context of detailed natural history data, we provide insight into the trade-offs faced by growing animals.

Sex ratio is variable and increasingly male biased at two colonies of Magellanic Penguins.

Sex ratios are commonly skewed and variable in wild populations, but few studies track temporal trends in this demographic parameter. We examined variation in the operational sex ratio at two protected and declining breeding colonies of Magellanic Penguins (Spheniscus magellanicus) in Chubut, Argentina. Penguins from the two colonies, separated by 105 km, migrate north in the non-breeding season and have overlapping distributions at sea. Conditions during the non-breeding season can impact long-term trends in operational sex ratio (i.e., through sex-specific survival) and interannual variation in operational sex ratio (i.e., through sex-specific breeding decisions). We found an increasingly male-biased operational sex ratio at the two disparate colonies of Magellanic Penguins, which may contribute to continued population decline. We also found that the two colonies showed synchronous interannual variation in operational sex ratio, driven by variation in the number of females present each year. This pattern may be linked to sex-specific overwintering effects that cause females to skip breeding, i.e., to remain at sea rather than returning to the colony to breed, more often than males. Contrary to our predictions, colony-wide reproductive success was not lower in years with a more male-biased operational sex ratio. We did find that males showed more evidence of fighting and were less likely to pair when the operational sex ratio was more male biased. Our results highlight an indirect mechanism through which variation in the operational sex ratio can influence populations, through a higher incidence of fighting among the less abundant sex. Because biased sex ratios can reduce the size of the breeding population and influence rates of conflict, tracking operational sex ratio is critical for conservation.

Lateralization (handedness) in Magellanic penguins.

Lateralization, or asymmetry in form and/or function, is found in many animal species. Brain lateralization is considered adaptive for an individual, and often results in "handedness," "footedness," or a side preference, manifest in behavior and morphology. We tested for lateralization in several behaviors in a wild population of Magellanic penguins Spheniscus magellanicus breeding at Punta Tombo, Argentina. We found no preferred foot in the population (each penguin observed once) in stepping up onto an obstacle: 53% stepped up with the right foot, 47% with the left foot (n = 300, binomial test p = 0.27). We found mixed evidence for a dominant foot when a penguin extended a foot for thermoregulation, possibly depending on the ambient temperature (each penguin observed once). Penguins extended the right foot twice as often as the left foot (n = 121, p < 0.0005) in 2 years when we concentrated our effort during the heat of the day. In a third year when we observed penguins early and late in the day, there was no preference (n = 232, p = 0.59). Penguins use their flippers for swimming, including searching for and chasing prey. We found morphological evidence of a dominant flipper in individual adults: 60.5% of sternum keels curved one direction or the other (n = 76 sterna from carcasses), and 11% of penguins had more feather wear on one flipper than the other (n = 1217). Right-flippered and left-flippered penguins were equally likely in both samples (keels: p = 0.88, feather wear: p = 0.26), indicating individual but not population lateralization. In fights, aggressive penguins used their left eyes preferentially, consistent with the right side of the brain controlling aggression. Penguins that recently fought (each penguin observed once) were twice as likely to have blood only on the right side of the face (69%) as only on the left side (31%, n = 175, p < 0.001). The proportion of penguins with blood only on the right side increased with the amount of blood. In most fights, the more aggressive penguin used its left eye and attacked the other penguin's right side. Lateralization depended on the behavior tested and, in thermoregulation, likely on the temperature. We found no lateralization or mixed results in the population of Magellanic penguins in three individual behaviors, stepping up, swimming, and thermoregulation. We found lateralization in the population in the social behavior fighting.

Important At-Sea Areas of Colonial Breeding Marine Predators on the Southern Patagonian Shelf.

The Patagonian Shelf Large Marine Ecosystem supports high levels of biodiversity and endemism and is one of the most productive marine ecosystems in the world. Despite the important role marine predators play in structuring the ecosystems, areas of high diversity where multiple predators congregate remains poorly known on the Patagonian Shelf. Here, we used biotelemetry and biologging tags to track the movements of six seabird species and three pinniped species breeding at the Falkland Islands. Using Generalized Additive Models, we then modelled these animals' use of space as functions of dynamic and static environmental indices that described their habitat. Based on these models, we mapped the predicted distribution of animals from both sampled and unsampled colonies and thereby identified areas where multiple species were likely to overlap at sea. Maximum foraging trip distance ranged from 79 to 1,325 km. However, most of the 1,891 foraging trips by 686 animals were restricted to the Patagonian Shelf and shelf slope, which highlighted a preference for these habitats. Of the seven candidate explanatory covariates used to predict distribution, distance from the colony was retained in models for all species and negatively affected the probability of occurrence. Predicted overlap among species was highest on the Patagonian Shelf around the Falkland Islands and the Burdwood Bank. The predicted area of overlap is consistent with areas that are also important habitat for marine predators migrating from distant breeding locations. Our findings provide comprehensive multi-species predictions for some of the largest marine predator populations on the Patagonian Shelf, which will contribute to future marine spatial planning initiatives. Crucially, our findings highlight that spatially explicit conservation measures are likely to benefit multiple species, while threats are likely to impact multiple species.

Author Correction: Important At-Sea Areas of Colonial Breeding Marine Predators on the Southern Patagonian Shelf.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

High-coverage genomes to elucidate the evolution of penguins.

BACKGROUND: Penguins (Sphenisciformes) are a remarkable order of flightless wing-propelled diving seabirds distributed widely across the southern hemisphere. They share a volant common ancestor with Procellariiformes close to the Cretaceous-Paleogene boundary (66 million years ago) and subsequently lost the ability to fly but enhanced their diving capabilities. With ∼20 species among 6 genera, penguins range from the tropical Galápagos Islands to the oceanic temperate forests of New Zealand, the rocky coastlines of the sub-Antarctic islands, and the sea ice around Antarctica. To inhabit such diverse and extreme environments, penguins evolved many physiological and morphological adaptations. However, they are also highly sensitive to climate change. Therefore, penguins provide an exciting target system for understanding the evolutionary processes of speciation, adaptation, and demography. Genomic data are an emerging resource for addressing questions about such processes. RESULTS: Here we present a novel dataset of 19 high-coverage genomes that, together with 2 previously published genomes, encompass all extant penguin species. We also present a well-supported phylogeny to clarify the relationships among penguins. In contrast to recent studies, our results demonstrate that the genus Aptenodytes is basal and sister to all other extant penguin genera, providing intriguing new insights into the adaptation of penguins to Antarctica. As such, our dataset provides a novel resource for understanding the evolutionary history of penguins as a clade, as well as the fine-scale relationships of individual penguin lineages. Against this background, we introduce a major consortium of international scientists dedicated to studying these genomes. Moreover, we highlight emerging issues regarding ensuring legal and respectful indigenous consultation, particularly for genomic data originating from New Zealand Taonga species. CONCLUSIONS: We believe that our dataset and project will be important for understanding evolution, increasing cultural heritage and guiding the conservation of this iconic southern hemisphere species assemblage.

Magellanic penguin telomeres do not shorten with age with increased reproductive effort, investment, and basal corticosterone.

All species should invest in systems that enhance longevity; however, a fundamental adult life-history trade-off exists between the metabolic resources allocated to maintenance and those allocated to reproduction. Long-lived species will invest more in reproduction than in somatic maintenance as they age. We investigated this trade-off by analyzing correlations among telomere length, reproductive effort and output, and basal corticosterone in Magellanic penguins (Spheniscus magellanicus). Telomeres shorten with age in most species studied to date, and may affect adult survival. High basal corticosterone is indicative of stressful conditions. Corticosterone, and stress, has been linked to telomere shortening in other species. Magellanic penguins are a particularly good model organism for this question as they are an unusually long-lived species, exceeding their mass-adjusted predicted lifespan by 26%. Contrary to our hypothesis, we found adults aged 5 years to over 24 years of age had similar telomere lengths. Telomeres of adults did not shorten over a 3-year period, regardless of the age of the individual. Neither telomere length, nor the rate at which the telomeres changed over these 3 years, correlated with breeding frequency or investment. Older females also produced larger volume clutches until approximately 15 years old and larger eggs produced heavier fledglings. Furthermore, reproductive success (chicks fledged/eggs laid) is maintained as females aged. Basal corticosterone, however, was not correlated with telomere length in adults and suggests that low basal corticosterone may play a role in the telomere maintenance we observed. Basal corticosterone also declined during the breeding season and was positively correlated with the age of adult penguins. This higher basal corticosterone in older individuals, and consistent reproductive success, supports the prediction that Magellanic penguins invest more in reproduction as they age. Our results demonstrate that telomere maintenance may be a component of longevity even with increased reproductive effort, investment, and basal corticosterone.

Telomeres shorten and then lengthen before fledging in Magellanic penguins (Spheniscus magellanicus).

For all species, finite metabolic resources must be allocated toward three competing systems: maintenance, reproduction, and growth. Telomeres, the nucleoprotein tips of chromosomes, which shorten with age in most species, are correlated with increased survival. Chick growth is energetically costly and is associated with telomere shortening in most species. To assess the change in telomeres in penguin chicks, we quantified change in telomere length of wild known-age Magellanic penguin (Spheniscus magellanicus) chicks every 15 days during the species' growth period, from hatching to 60 days-of-age. Magellanic penguins continue to grow after fledging so we also sampled a set of 1-year-old juvenile penguins, and adults aged 5 years. Telomeres were significantly shorter on day 15 than on hatch day but returned to their initial length by 30 days old and remained at that length through 60 days of age. The length of telomeres of newly hatched chicks, chicks aged 30, 45 and 60 days, juveniles, and adults aged 5 years were similar. Chicks that fledged and those that died had similar telomere lengths. We show that while telomeres shorten during growth, Magellanic penguins elongate telomeres to their length at hatch, which may increase adult life span and reproductive opportunities.

Chronic oil pollution harms Magellanic penguins in the Southwest Atlantic.

Petroleum pollution is a problem for seabirds along the Southwest Atlantic coast. Twenty-five groups from Salvador, Brazil (12 degrees 58'S) to San Antonio Oeste, Argentina (40 degrees 43'S) survey or rehabilitate sick or oiled seabirds. Four groups, one each in Brazil and Uruguay, and two in Argentina, kept counts of birds found alive and in need of rehabilitation. An average of 63.7% of the seabirds found were Magellanic penguins (Spheniscus magellanicus), with 3869 reported since 1987. Mainly adult penguins were found in Argentina (1605 of 2102 penguins of known age class) and Uruguay (158 of 197). Juveniles were most common in Brazil (234 of 325). Oil fouling was the most frequent cause of injury or sickness. The number of oiled penguins reported in their wintering range has greatly increased since the early 1990s and is strongly correlated with petroleum exports from Argentina. Our results show that chronic petroleum pollution is a problem for wildlife from Southern Brazil through Northern Argentina, and regulations and enforcement are failing to protect living resources.

Age and food deprivation affects expression of the glucocorticosteroid stress response in Magellanic penguin (Spheniscus magellanicus) chicks.

We examined how the glucocortical stress response in free-living Magellanic penguin (Spheniscus magellanicus) chicks changes with age and whether adrenocortical function of chicks within a brood varies in relation to food provisioned by adults. Chicks showed little corticosterone response to capture stress shortly after hatching, an intermediate response around 45-d posthatch, and a robust stress response near fledging. However, in response to an adrenocorticotropic hormone (ACTH) challenge, hatchlings were capable of secreting corticosterone at adult-like levels. The larger sibling in broods of two showed a similar gradual stress-response development pattern. In contrast, by day 45, when differences in body condition were well established between siblings, the smaller, food-deprived chicks significantly increased baseline levels of corticosterone but showed normal stress-induced levels. Near fledging, baseline levels had returned to normal, but stress-induced levels were lower than expected. Similar to altricial species, normally developing semialtricial Magellanic penguin chicks do not express a robust corticosterone stress response until near fledging. Chronic stressors such as food deprivation cause corticosterone use to be up-regulated earlier than expected. However, in cases of extended chronic stress, down-regulation may ensue, thus avoiding the negative effects of chronically elevated levels of corticosterone.