Seabirds face increasing pressure from commercial fisheries through both direct mortality and indirect competition for shared prey resources. In Chile’s Humboldt Current System, artisanal purse-seine fisheries target small pelagic fish species such as anchoveta (Engraulis ringens), which also comprise key components of the Humboldt penguin’s (Spheniscus humboldti) diet. To investigate the potential for spatio-temporal overlap between purse-seine fisheries and penguin foraging areas, we tracked breeding Humboldt penguins from Isla Choros, Coquimbo Region, northern Chile, during the autumn and spring breeding seasons of 2022 using GPS dive loggers. We quantified penguin at-sea distribution and overlap with fishing effort data obtained from purse-seine vessels operating in the Coquimbo Region. Tracking data from 22 penguins revealed a bimodal foraging pattern linked to nest location. Penguins nesting on the eastern, mainland-facing side of Isla Choros foraged exclusively in coastal waters, while western-nesting individuals foraged both offshore and inshore, likely depending on environmental conditions. Kernel Density Estimation (KDE) analysis identified two core foraging zones: one along the mainland coast near Playa de los Choros and another southwest of the island. Purse-seine fishing effort in autumn was concentrated along the coast, overlapping substantially with the coastal foraging zone of the penguins. Nearly 60% of the penguins’ coastal core foraging area overlapped with the 50% KDE of autumn purse-seine activity. In contrast, spring fishing effort was more dispersed and located farther south, with no overlap observed between spring fishing and penguin foraging areas. These findings suggest a high likelihood of indirect resource competition between Humboldt penguins and fisheries during the autumn breeding season—a critical time when penguins are energetically constrained as central place foragers. We provide the first empirical evidence of substantial seasonal overlap between Humboldt penguins and inshore purse-seine fisheries at the Humboldt Archipelago and highlight the need to integrate seabird ecology into fisheries management. To protect vulnerable seabird populations such as the Humboldt penguin, marine spatial planning should consider critical foraging habitats and breeding schedules. Future work should aim to quantify dietary overlap, assess potential sub-lethal effects of prey depletion, and monitor the impact of small-scale, untracked fisheries within key penguin foraging areas.

Human-induced rapid environmental change increasingly causes animals to select habitats of poor quality based on misleading cues, creating ecological traps that drive demographic decline and elevate extinction risk. Yet research on ecological traps has focused mainly on terrestrial and freshwater systems, while marine traps-particularly those linked to fisheries, the dominant marine industry and a potential source of traps for seabirds and other vertebrates-remain understudied. In this marine context, fisheries represent a double-edged sword for seabirds: the trophic subsidies they provide (bait, discards, and catches) offer predictable food but also attract birds to vessels, thereby increasing their risk of mortality from bycatch. Here, we analyze the interaction between seabirds' scavenging behavior and bycatch in fisheries, as well as the effect of the slow-fast life-history continuum on their vulnerability to ecological traps. Through a systematic literature review and Bayesian multilevel models accounting for phylogenetic relatedness (341 species), we show a clear preference-performance mismatch: slow-lived seabirds, such as albatrosses, are more likely to exploit fishery-derived trophic subsidies and are consequently more threatened by bycatch. Building on recent evidence that ecological traps are a common phenomenon in marine ecosystems, we propose that they should be recognized as a primary mechanism underlying seabird-fishery interactions. Moreover, incorporating ecological traps into theoretical frameworks could strengthen ecosystem-based fisheries management by clarifying the causes and consequences of fishery impacts on seabirds, enhancing the effectiveness of management and conservation strategies, and supporting the enforcement of mitigation measures.

La caracterización del tránsito aéreo de avifauna es un requisito para evaluar el impacto ambiental de proyectos que generan obstáculos al desplazamiento de las aves (e.g., aerogeneradores, torres y líneas de transmisión eléctrica). Para esto, la autoridad ambiental chilena recomienda metodologías de observación directa, es decir, la determinación visual y/o auditiva de las variables de interés por un equipo de personas en terreno. Estas metodologías están sujetas a los sesgos propios del observador y a los esfuerzos de muestreo, muchas veces definidos por aspectos laborales y económicos. Esto plantea la necesidad de incorporar metodologías automatizadas, como el radar, para lograr caracterizaciones más precisas. En este estudio comparamos seis variables de tránsito aéreo de avifauna (especie, número, velocidad, dirección, altura y longitud de los vuelos) obtenidas de forma simultánea por un grupo de observadores y un radar marítimo. El radar obtuvo significativamente más registros que los observadores en el número de individuos, dirección y altura de vuelo. La velocidad y longitud de trayectoria sólo fueron registradas por el radar, no así por los observadores. La determinación de la especie fue la única variable donde los datos proporcionados por el radar no permitieron una identificación, pero sí la experiencia de los observadores. Estos resultados indican que la caracterización de tránsito aéreo de avifauna, tal como se está haciendo en la actualidad, no está aportando información precisa para la toma de decisiones sobre la viabilidad ambiental de los proyectos, y sería recomendable implementar de forma progresiva el uso de radar en estos estudios de evaluación ambiental.

Reliable, up-to-date assessments of population status and trends are essential for effective conservation. For the four Spheniscus penguin species, these are often undermined by methodological and logistical constraints due to their unique breeding ecology (e.g., burrow nesting and asynchronous breeding). As a result, no single survey method is universally applicable across the genus. Moreover, uneven sampling effort, inconsistent survey protocols, and variable data quality across countries and research groups further obscure true demographic patterns and complicate interpretations across species and regions. In consequence, population trends for these species—among the world’s most threatened seabirds—are frequently uncertain or contradictory, limiting our ability to propose effective management actions. Here, we summarize the current challenges faced by researchers working across the ranges of Humboldt, African, Magellanic, and Galápagos penguins. We discuss pitfalls associated with extrapolating from non-representative colonies, integrating disparate data types, and interpreting trends in the context of climate-driven variability and threats. Finally, we propose a suite of solutions to strengthen future assessments and improve consistency and accuracy. Overall, we aim to chart a collaborative path toward more robust, comparable, and effective conservation assessments for these penguins as well as other seabirds.

The relative importance of genetic drift and local adaptation in facilitating speciation remains unclear. This is particularly true for seabirds, which can disperse over large geographic distances, providing opportunities for intermittent gene flow among distant colonies that span the temperature and salinity gradients of the oceans. Here, we delve into the genomic basis of adaptation and speciation of banded penguins, Galápagos (Spheniscus mendiculus), Humboldt (Spheniscus humboldti), Magellanic (Spheniscus magellanicus), and African penguins (Spheniscus demersus), by analyzing 114 genomes from the main 16 breeding colonies. We aim to identify the molecular mechanism and genomic adaptive traits that have facilitated their diversifications. Through positive selection and gene family expansion analyses, we identified candidate genes that may be related to reproductive isolation processes mediated by ecological thermal niche divergence. We recover signals of positive selection on key loci associated with spermatogenesis, especially during the recent peripatric divergence of the Galápagos penguin from the Humboldt penguin. High temperatures in tropical habitats may have favored selection on loci associated with spermatogenesis to maintain sperm viability, leading to reproductive isolation among young species. Our results suggest that genome-wide selection on loci associated with molecular pathways that underpin thermoregulation, osmoregulation, hypoxia, and social behavior appears to have been crucial in local adaptation of banded penguins. Overall, these results contribute to our understanding of how the complexity of biotic, but especially abiotic, factors, along with the high dispersal capabilities of these marine species, may promote both neutral and adaptive lineage divergence even in the presence of gene flow.

Grey Gulls (Leucophaeus modestus) are unique among gulls in that they forage in the coast but breed up to 115 km inland in the barren Atacama Desert of northern Chile. By nesting in the desert, adults are limited to a single daily foraging trip to feed their chicks and relieve their incubating/brooding mates. Birds perform long-distance and energetically expensive trips between foraging and breeding grounds. We describe how Grey Gulls modify nest attendance and chick provisioning strategies from an unusual coastal colony established at Playa Brava, northern Chile, during the 2017-2018 season. Contrary to what it is usually observed in desert colonies, incubating, and brooding Grey Gulls at Playa Brava relieved mates at the nest regularly and fed chicks several times throughout the day. Some adults even left their chicks unattended at the nest to forage on the nearby shoreline (<0.15 km) for a variable amount of time (up to 57 min) before returning to resume brooding. These behaviours are likely to ease parental duties by allowing multiple pair changeovers, reduce energy expenditure by avoiding extensive trips between the desert and the coast, increase chick growth rates by allowing multiple meals during the day, among other advantages. Our observations show that, when moving their colonies from the desert to the coast, Grey Gulls accordingly adjust their breeding behaviour to cope with this new habitat.

Animals constantly test the borders of their own ecological niche and tend to expand their range, which is now additionally challenged by global climate change. Following human exploitation throughout the Southern Ocean in the 19th and the beginning of the 20th century, numbers of King Penguin breeding pairs have increased and former breeding sites have been re-colonized. Since 2010 a breeding colony became (re-)established at Bahía Inútil, Strait of Magellan, Tierra del Fuego, Chile. The aims of this study were to study the foraging ecology of King Penguins at this new breeding site, which is characterized by a set of different environmental variables as it is located within the confined environment of the Magellan Strait, more than 300 km from the open ocean. During the course of this study, thirty-two birds were successfully equipped with external devices that recorded 206 foraging trips by breeding and non-breeding birds. With one exception, all birds foraged throughout the year exclusively in the Magellan Strait with the main foraging areas located within 100 km from the colony. The diving activities of 15 King Penguins were recorded during 59 foraging trips, the deepest dive was 160 m and the longest dive lasted 6.75 mins. Based on a representative subsample of 3000 dives, mean dive depth was 32 ± 34 m and mean dive duration 117 ± 84 s. Accordingly, foraging trip durations throughout the year were significantly shorter than those recorded for conspecifics elsewhere. In accordance with these changes in foraging behavior, stomach contents from seven birds showed a mix of fish and squid, with Falkland sprats Sprattus fuegensis as the main prey item present in all samples. The implications of these behavioral adaptations are discussed with regard to this unusual confined foraging environment and predicted changes in the performance of King Penguins breeding elsewhere following global change.

The Chilean coast holds a high seabird diversity and also extensive fisheries that interact with birds producing bycatch. We used data on beached seabirds reported by news media to depict spatial and temporal patterns of fishery-related seabird mortality and correlated these data with the spatial and temporal fishing effort of the three main purse-seine fleets operating in south-central Chile (33 to 40 degrees S). Between 2005 and 2019 we detected 97 mortality events reporting >19,000 beached seabirds attributed to bycatch. Mortality was recorded between 18 and 53 degrees S (similar to 3800 km of coastline), affecting 16 seabird species, with 90% concentrated between 33 and 40 degrees S (800 km), exactly where purse-seine fleets operate. Sooty shearwater (Ardenna grisea) comprised 70% of all dead birds recorded. Magellanic penguins (Spheniscus magellanicus) and guanay cormorants (Phalacrocorax boungainvillii) were also affected. Mortality events of Sooty shearwaters was highest (P < 0.001) between February and May (54%) and October-November (36%), coinciding with the timing of the species migratory movements; shearwater mortality was particularly high at 36-37 degrees S (50%) and 39-40 degrees S (36%). Sooty shearwater mortality presented a very high spatial overlap (93%) and significant temporal correlation (0.64) with combined industrial and artisanal purse-seine fishing effort targeting on Peruvian anchovy (Engraulis ringens) and Araucanian herring (Strangomera bentincki). Our study shows when and where seabirds are more susceptible to mortality due to interactions with fisheries along the Chilean coast. This information could be used by authorities to regulate the fishing activity and focus conservation efforts to the most affected species at the appropriate spatial and temporal scales.

ABSTRACT The Kelp Gull (Larus dominicanus) is a widespread and abundant seabird species inhabiting much of the southern hemisphere, where at least 6 subspecies are recognized. For the nominate subspecies L. d. dominicanus present in South America, limited information is available on its basic life history traits. In this note we present information on longevity and philopatry based on the resighting of 3 Kelp Gull individuals banded as chicks at their natal colony in central Chile. All birds returned to breed at their natal island and established their nests within 50–80 m of their natal subcolony. Maximum observed longevity ranged between 17.5 and 22.1 years. We consider this information on life history and behavior valuable for management purposes as this subspecies is rapidly increasing at some coastal regions of South America and it may become a problematic species to humans and other seabird populations.

The upwelling hypothesis has been proposed to explain reduced or lack of population structure in seabird species specialized in food resources available at cold-water upwellings. However, population genetic structure may be challenging to detect in species with large population sizes, since variation in allele frequencies are more robust under genetic drift. High gene flow among populations, that can be constant or pulses of migration in a short period, may also decrease power of algorithms to detect genetic structure. Penguin species usually have large population sizes, high migratory ability but philopatric behavior, and recent investigations debate the existence of subtle population structure for some species not detected before. Previous study on Humboldt penguins found lack of population genetic structure for colonies of Punta San Juan and from South Chile. Here, we used mtDNA and nuclear markers (10 microsatellites and RAG1 intron) to evaluate population structure for 11 main breeding colonies of Humboldt penguins, covering the whole spatial distribution of this species. Although mtDNA failed to detect population structure, microsatellite loci and nuclear intron detected population structure along its latitudinal distribution. Microsatellite showed significant Rst values between most of pairwise locations (44 of 56 locations, Rst = 0.003 to 0.081) and 86% of individuals were assigned to their sampled colony, suggesting philopatry. STRUCTURE detected three main genetic clusters according to geographical locations: i) Peru; ii) North of Chile; and iii) Central-South of Chile. The Humboldt penguin shows signal population expansion after the Last Glacial Maximum (LGM), suggesting that the genetic structure of the species is a result of population dynamics and foraging colder water upwelling that favor gene flow and phylopatric rate. Our findings thus highlight that variable markers and wide sampling along the species distribution are crucial to better understand genetic population structure in animals with high dispersal ability.

More than half of the world's 18 penguin species are declining. We, the Steering Committee of the International Union for Conservation of Nature Species Survival Commission Penguin Specialist Group, determined that the penguin species in most critical need of conservation action are African penguin (Spheniscus demersus), Galápagos penguin (Spheniscus mendiculus), and Yellow-eyed penguin (Megadyptes antipodes). Due to small or rapidly declining populations, these species require immediate scientific collaboration and policy intervention. We also used a pairwise-ranking approach to prioritize research and conservation needs for all penguins. Among the 12 cross-taxa research areas we identified, we ranked quantifying population trends, estimating demographic rates, forecasting environmental patterns of change, and improving the knowledge of fisheries interactions as the highest priorities. The highest ranked conservation needs were to enhance marine spatial planning, improve stakeholder engagement, and develop disaster-management and species-specific action plans. We concurred that, to improve the translation of science into effective conservation for penguins, the scientific community and funding bodies must recognize the importance of and support long-term research; research on and conservation of penguins must expand its focus to include the nonbreeding season and juvenile stage; marine reserves must be designed at ecologically appropriate spatial and temporal scales; and communication between scientists and decision makers must be improved with the help of individual scientists and interdisciplinary working groups.

Breeding status directly affects the at-sea behaviour of seabirds, resulting in marked differences between breeding and non-breeding birds. In this study, we report for the first time the foraging and diving behaviour of coexisting incubating, courting and non-breeding King Penguins (Aptenodytes patagonicus) at a recently established colony in Tierra del Fuego, Chile, to determine differences in (1) the number and duration of the foraging trips, (2) time spent at sea and on land, and (3) diving performance and foraging success. We obtained data from four incubating, five courting and three non-breeding penguins equipped with time-depth recorders during November and December 2014. Incubating birds performed a single but long trip (8.1 +/- 1.9 days), while courting birds performed one or two trips of intermediate duration (2.3 +/- 0.8 days) and non-breeders made multiple short trips (0.6 +/- 0.1 days). Courting birds spent a significantly greater proportion of their time on land than the other birds. Incubating birds performed the deepest and longest dives and had the highest diving efficiency, while non-breeders performed the shallowest and shortest dives and exhibited low diving efficiencies, suggesting that birds are utilising different foraging areas. These results indicate that incubating, courting and non-breeding King Penguins, although coexisting temporally at the same colony, differentially adjust their foraging and diving behaviour, most likely to accomplish their specific social and energetic demands.

Worldwide, in recent years capture fisheries targeting lower-trophic level forage fish and euphausiid crustaceans have been substantial (similar to 20 million metric tons [MT] annually). Landings of forage species are projected to increase in the future, and this harvest may affect marine ecosystems and predator-prey interactions by removal or redistribution of biomass central to pelagic food webs. In particular, fisheries targeting forage fish and euphausiids may be in competition with seabirds, likely the most sensitive of marine vertebrates given limitations in their foraging abilities (ambit and gape size) and high metabolic rate, for food resources. Lately, apparent competition between fisheries and seabirds has led to numerous high-profile conflicts over interpretations, as well as the approaches that could and should be used to assess the magnitude and consequences of fisheries sea-bird resource competition. In this paper, we review the methods used to date to study fisheries competition with seabirds, and present "best practices" for future resource competition assessments. Documenting current fisheries competition with seabirds generally involves addressing two major issues: 1) are fisheries causing localized prey depletion that is sufficient to affect the birds? (i.e., are fisheries limiting food resources?), and 2) how are fisheries-induced changes to forage stocks affecting seabird populations given the associated functional or numerical response relationships? Previous studies have been hampered by mismatches in the scale of fisheries, fish, and seabird data, and a lack of causal understanding due to confounding by climatic and other ecosystem factors (e.g., removal of predatory fish). Best practices for fisheries-seabird competition research should include i) clear articulation of hypotheses, ii) data collection (or summation) of fisheries, fish, and seabirds on matched spatio-temporal scales, and integration of observational and experimental (including numerical simulation) approaches to establish connections and causality between fisheries and seabirds. As no single technique can provide all the answers to this vexing issue, an integrated approach is most promising to obtain robust scientific results and in turn the sustainability of forage fish fisheries from an ecosystem perspective.

Penguins are the most threatened group of seabirds after albatrosses. Although penguins are regularly captured in fishing gear, the threat to penguins as a group has not yet been assessed. We reviewed both published and grey literature to identify the fishing gear types that penguins are most frequently recorded in, the most impacted species and, for these susceptible species, the relative importance of bycatch compared to other threats. While quantitative estimates of overall bycatch levels are difficult to obtain, this review highlights that, of the world's 18 species of penguins, 14 have been recorded as bycatch in fishing gear and that gillnets, and to a lesser extent trawls, are the gear types that pose the greatest threats to penguins. Bycatch is currently of greatest concern for yellow-eyed Megadyptes antipodes (Endangered), Humboldt Spheniscus humboldti (Vulnerable) and Magellanic Spheniscus magellanicus penguins (Near Threatened). Penguins face many threats; reducing bycatch mortality in fishing gear will greatly enhance the resilience of penguin populations to threats from habitat loss and climate change that are more difficult to address in the short term. Additional data are required to quantify the true extent of penguin bycatch, particularly for the most susceptible species. In the meantime, it is crucially important to manage the fisheries operating within known penguin foraging areas to reduce the risks to this already threatened group of seabirds.

Penguins are the most threatened group of seabirds after albatrosses. Although penguins are regularly captured in fishing gear, the threat to penguins as a group has not yet been assessed. We reviewed both published and grey literature to identify the fishing gear types that penguins are most frequently recorded in, the most impacted species and, for these susceptible species, the relative importance of bycatch compared to other threats. While quantitative estimates of overall bycatch levels are difficult to obtain, this review highlights that, of the world’s 18 species of penguins, 14 have been recorded as bycatch in fishing gear and that gillnets, and to a lesser extent trawls, are the gear types that pose the greatest threats to penguins. Bycatch is currently of greatest concern for yellow-eyed Megadyptes antipodes (Endangered), Humboldt Spheniscus humboldti (Vulnerable) and Magellanic Spheniscus magellanicus penguins (Near Threatened). Penguins face many threats; reducing bycatch mortality in fishing gear will greatly enhance the resilience of penguin populations to threats from habitat loss and climate change that are more difficult to address in the short term. Additional data are required to quantify the true extent of penguin bycatch, particularly for the most susceptible species. In the meantime, it is crucially important to manage the fisheries operating within known penguin foraging areas to reduce the risks to this already threatened group of seabirds.

Easter Island is located in the southeastern corner of Polynesia. This 163.6 km(2) volcanic island is one of the most isolated places on Earth. During spring 2014 and 2015, we studied a breeding colony of Red-tailed Tropicbirds (Phaethon rubricauda) located on Rano Raraku Volcano. We specifically aimed to determine (1) main nest types used by tropicbirds, (2) nest distribution and abundance, (3) breeding success, and (4) threats faced by tropicbirds at this colony. Results showed presence of four nest types: rock caves, moai nest, rock protected, and vegetation nests. Nests were strongly associated with unfinished moai statues. Breeding success ranged from 37% in 2014 to 26% in 2015. Camera traps and direct observations showed interactions with five invasive alien species: the raptor Chimango Caracara (Milvago chimango) was the most severe predator of unattended eggs and chicks; cats were observed close to adult birds; dogs killed fledglings; ants preyed on newborn chicks; rats were recorded inspecting both occupied and unoccupied nests. We suggest that this is a relatively new and expanding colony. Urgent measures to control and/or eradicate invasive alien species on Rano Raraku are needed to improve breeding success and persistence of this colony in the future.

The Gray Gull (Leucophaeus modestus) has the unique habit among gulls of nesting in the interior Atacama Desert, up to 100 km from the coast. During the 2014-2015 austral breeding season, two breeding colonies were recorded on the coast within 90 m of the shoreline in the Antofagasta Region, northern Chile. The new colonies ranged in size from 40 (Playa Grande) to 150 (Playa Brava) nests. Egg laying was synchronous in both colonies and most likely occurred in late November 2014, coinciding with egg laying in desert colonies. The colony at Playa Brava was successful, but the one at Playa Grande was deserted due to feral dog (Canis familiaris) attacks. The habitat used by Gray Gulls resembled that reported for desert colonies, with flat plains covered with small rocks, which provide protection to chicks from intense solar radiation. This unusual coastal nesting behavior could result in the modification of certain life history and behavioral traits in the Gray Gull (e.g., chick growth rates, energy expenditure, and foraging ranges), which have evolved to breed in severe desert conditions. We suggest that coastal breeding is adopted by Gray Gulls during El Nino years in response to reduced food supply. During El Nino years, Gray Gulls would move to the coast where access to food is better and thermoregulatory costs are lower, but predation is higher. During non-El Nino years, Gray Gulls would resume their ancestral desert-nesting strategy in which traveling distances between the coast and nesting grounds are considerable and thermoregulatory costs are higher, but predation risks are lower. Future observations should confirm if Gray Gulls continue breeding at coastal sites during El Nino years or if this becomes a regular behavior independent of oceanographic conditions.

In order to enhance foraging efficiency, seabirds usually use local enhancement to locate their patchy prey, triggering the formation of multispecies feeding flocks (MSFFs). Although MSFFs have been widely documented, few studies have attempted to describe the temporal stability of species composition within MSFFs and which intrinsic factors (i.e., taxonomic identity, foraging guild, migratory timing, migratory origin, and body size) are involved. Using an 8-year (2006-2014) database of monthly seabird counts at an upwelling zone within the Humboldt Current in central Chile (33S), we showed that MSFF compositional stability varies seasonally, with more than 1 intrinsic factor involved. On the basis of the network analysis and null models, we showed that during austral winter taxonomic affinities are most likely to be determinant, with a high assortativity within Procellariiformes and among Charadriiformes species. During austral spring, foraging affinities are more important with a high assortativity within foraging guilds (surface feeders and pursuit divers). Timing and origin of migration scarcely explain species assortativity, whereas body size demonstrates to be an important trait, probably related with competitive skills. On the basis of assemblage stability, we suggest that during migration (austral autumn and spring) and reproductive seasons (austral summer), foraging seabirds associate randomly (within phenotypically or behaviorally similar species). During winter, species exhibited strong preferences to associate within taxonomic groups and presented the highest reassociation probability. This study demonstrates that MSFF, rather than being constituted by birds randomly aggregated at a food source, are most likely formed and structured by intrinsic traits whose relative importance shifts seasonally.

Ten Humboldt (Spheniscus humboldti) and eight Magellanic Penguins (S. magellanicus) were successfully equipped with satellite transmitters in March 2009 on Islotes Puñihuil in central south-Chile to follow their post-moult dispersal. Overall, Humboldt Penguins could be followed for a mean period of 49 ±18 days (range: 25–93) and Magellanic Penguins for 57 ±12 days (range 35–68). Irrespective of species and sex, seven study birds remained in the vicinity of their breeding ground throughout the transmission period. All other penguins moved northwards, either only a relatively short distance (max 400 km) to Isla Mocha at 38°S (n=3) or further north beyond 35°S (n=8). However, eight of these birds (73%) turned south again towards the end of the individual tracking periods. The total area used by both species during the tracking period was restricted to a coastal area stretching from the breeding site at 42°S about 1000 km to the north at about 32°S. The area used by Humboldt penguins overlapped by 95% the area used by Magellanic penguins, whereas the area used by the latter species was much larger and overlapped only by 45% with the area used by Humboldt penguins. Overall, our results indicate that Magellanic Penguins in the Pacific Ocean are probably less migratory than their conspecifics on the Atlantic side, while Humboldt Penguins appear to be more migratory than previously anticipated. In general, there was a poor relationship between preferred foraging areas and chlorophyll-a, as a proxy for primary productivity, indicating the limitations of using remote-sensed primary productivity as a proxy to interpret the foraging behaviour of marine predators. In addition, there was also no clear relationship between the preferred foraging areas and the amount of regional fish catches by artisanal fishery.