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The Sooty Shearwater (Ardenna grisea) is a species facing global decline, nesting on southern hemisphere islands, and migrating to the northern hemisphere during the non-breeding season. Historical groundwork on Wollaston Island in Chile suggested a possible dispersion of breeding grounds along the seaward fringe of the Fuegian islands, including Isla de los Estados. Recent records ranked the species as the second most abundant during the summer near Isla de los Estados, emphasizing the need for continued exploration to locate and understand the potential breeding site on the island. This study confirms the species ́ breeding presence on Isla de los Estados in the Fuegian archipelago, Argentina. Additionally, we present a preliminary evaluation of its habitat utilization. Active burrows were found along the northern coast of the island on slopes with dense, stumpy subantarctic forests and beneath or alongside rocky outcrops overlooking the coast. Future research should aim at estimating the total population for Isla de los Estados, explore habitat use, and gain insights into the year-round distribution of sooty shearwaters at sea for formulating effective conservation strategies. [ABSTRACT FROM AUTHOR]

Seabirds coexist within colonies yet the role of conspecifics, whilst foraging is still poorly understood. In the 2019/20 and 2020/21 breeding seasons Magellanic penguins Spheniscus magellanicus and Gentoo penguins Pygoscelis papua were equipped with video loggers and GPS devices (n = 3 and n = 2, respectively) or only GPS devices (n = 11 and n = 2) at Martillo Island (54°54′ S, 67°23′ W), Argentina and compared with GPS tracks from previous seasons (2014, 2015 and 2017). Magellanic penguins transited in groups with conspecifics to the feeding grounds (up to 13 individuals were recorded simultaneously) in search of pelagic Fuegian sprat Sprattus fuegensis, but then were not filmed in close company of conspecifics during prey capture. Gentoo penguins generally fed on Nototheniid sp. at the seafloor. Contrary to predictions, Gentoo penguins foraged with conspecifics in small groups of 2–4 individuals, they coordinated to dive down, search and ambush prey. Gentoo penguins were also recorded foraging pelagically on Fuegian sprat. Conspecifics play an important role either during the initial search for prey patches, particularly when searching for elusive pelagic prey or during the small-scale search and hunt for benthic prey hidden in the seafloor substrate. The presence of conspecifics seems to be important during foraging for Magellanic and Gentoo penguins and this may be reflecting a positive aspect of coloniality. [ABSTRACT FROM AUTHOR]

This paper provides data on a newly discovered colony of Magellanic penguins Spheniscus magellanicus in the southwest Atlantic Ocean. A new settlement was found while conducting southern rockhopper penguin Eudyptes chrysocome studies in the San Juan de Salvamento colony in Staten Island, Argentina. The colony holds 88 breeding pairs. While the origin of the founders was unknown, it is possible that they came from the nearby Observatorio Island colony located ~ 20 km away. New colonies allow populations to expand and establish in new areas, which could allow a species to respond to changes in climate. Nonetheless, this expansion might be a detriment to other penguin species that already occupied the area. [ABSTRACT FROM AUTHOR]

Mercury is a widely available pollutant associated with negative effects on wildlife, especially top predators. Here, we characterized the mercury concentrations in feathers of Striated Caracara Phalcoboenus australis on Isla de los Estados (Argentina). With feather mercury levels averaging 26.3 mg/kg, this population has the highest mean feather mercury ever reported for a bird population in South America. We propose that the high mercury concentrations are related to the feeding habits of the species: during feather moult, they are strongly associated with a Southern Rockhopper Penguin (Eudyptes chrysocome) colony known to be highly exposed to mercury contamination. Our results suggest that this Striated Caracara population should be monitored for acute effects and potential impacts of mercury toxicity. [ABSTRACT FROM AUTHOR]

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Breeding seabirds must balance self-care and reproduction, especially once offspring have hatched and have to be fed regularly. Seabirds may selectively provision chicks with higher quality food than they consume themselves. In contrast, adults may prioritize their survival rather than their progeny by feeding chicks with lower quality prey items than they feed themselves. We examined the parental provisioning strategies of southern rockhopper penguins at Isla de los Estados in 2012 using nitrogen (δ15N) and carbon (δ13C) stable isotope analysis to determine if selective provisioning and foraging habitat differences exist between parents and their offspring. We found that chicks had higher δ15N values compared to both male and female penguins, and female had slightly higher δ15N values compared to male penguins. There was also a strong positive relationship in δ15N values between female penguins and their offspring, indicating that chicks' diet resembles the female parent more than the male parent. Our results support the hypothesis of selective provisioning of chicks with higher trophic level (i.e., δ15N value) prey and the observation that females exclusively feed chicks during the guard stage. We did not find differences in δ13C values between adult and chicks suggesting no differences in the areas or habitats used to forage for self-provisioning and chick-provisioning. These findings likely have broader significance as provisioning rates and quality of food consumed by chicks is often strongly related to chick growth and survival. [ABSTRACT FROM AUTHOR]

Interannual variation in seabird foraging or reproductive behaviour may reflect fluctuations in marine resources. In this study, we evaluated different foraging and breeding parameters of Magellanic Penguins ( Spheniscus magellanicus) from Martillo Island in the Beagle Channel, and the relationships between these parameters at different stages within the season (incubation, early and late chick-rearing) over three consecutive breeding seasons (2006-2007, 2007-2008 and 2008-2009). In 2007, we observed greater adult foraging effort (longer foraging trip duration and vertical travel distance, VTD) and lower chick feeding frequency, together with a slower growth rate and later fledging date of chicks, which we suggest was linked to lower food availability near the colony that year. The increased foraging effort appeared to be compensated by enhanced feeding activity (e.g., number of wiggles per dive). However, this increase did not coincide with a larger amount of food load brought to colony, which may have been due to a change in the type or size of prey consumed by the penguins. Magellanic Penguins from Martillo Island showed great plasticity in foraging behaviour, as evidenced by changes in consumed prey type or increased foraging effort and feeding activity when the consumption of their main prey item, Sprattus fuegensis, seemed to decrease. Moreover, during this particular breeding season, although the growth rate of chicks was lower, the breeding success remained constant throughout the study period, suggesting that the penguins managed to compensate for the apparent decrease in Fuegian sprat. [ABSTRACT FROM AUTHOR]

Knowledge of seabirds' diet at each breeding site and its temporal variation is key to understanding and evaluating how changes in marine resources affect each seabird population. In this study, we determined the diet of Magellanic penguins (MP, Spheniscus magellanicus) at Martillo Island, accounting for sex, breeding stage and year. We analyzed a total of 144 stomach contents during three consecutive breeding seasons (2006-2007, 2007-2008 and 2008-2009) and stages (incubation, early and late chick-rearing). MP fed mainly on fuegian sprat ( Sprattus fuegensis), which represented 75 % of the biomass consumed by birds during the entire study. The next important prey was squat lobster ( Munida gregaria), followed by Patagonian squid ( Loligo gahi). Both sexes consumed similar prey items. We observed variation in diet relative composition among breeding years and stages. Fuegian sprat consumption decreased throughout the years whereas squat lobster increased. Penguins consumed a higher proportion of squat lobster and Patagonian squid during the incubation stage than in the chick-rearing stages, whereas fuegian sprat was almost the only prey item consumed during the late chick-rearing stage. MPs show certain flexibility in the use of resources probably as a response to changes in prey populations. Variability in the diet among different reproductive stages could be related to changes in the distribution and abundance of their main prey near the colony during the breeding season together with changes in the energy requirements of seabirds. [ABSTRACT FROM AUTHOR]

Understanding the dynamics and causes of population trends are essential for seabird conservation. Long-term studies of seabirds at high-latitude (Antarctic, sub-Antarctic and Arctic) regions have shown contrasting species-specific trends in population size in response to climate change and anthropogenic pressures. We have studied for the last 20 years (1992-2012) the population trends of seven seabird species that breed in the Beagle Channel, south-eastern Tierra del Fuego and at Staten Island, a sub-Antarctic region in southern Argentina. The numbers of Magellanic and Gentoo Penguins increased significantly since 1992 (by >15 % year). In comparison, the populations of Imperial Cormorants, Dolphin Gulls and Kelp Gulls increased at slower rates (<5 % year), while the Rock Cormorant population even decreased by 1.3 % year. At Staten Island, the numbers of Rockhopper Penguins decreased by 24 % between the censuses of 1998 and 2010, whereas the population of Magellanic Penguins increased by 227 % during the same period. Over the study period, air and sea-surface temperatures remained stable in our study area, suggesting that the detected population changes are not driven by the climate. This finding contrasts with the detected links between increasing temperature trends and seabird population changes reported from Antarctic and Arctic regions. The level of tourism and size of the permanent human population has increased in the Beagle Channel area during the last 20 years and could be responsible for the increase of gull populations. The seabird species that received the highest number of visitors (Imperial Cormorants and penguin species) seem to be adapted or at least indifferent to pressures exerted by tourism, as their populations increased during the study period. In addition, increasing numbers of seabirds in the area may generally be leading to higher abundances of scavenging species (e.g. gulls). [ABSTRACT FROM AUTHOR]

The time seabirds have to forage is restricted while breeding, as time at sea must be balanced against the need to take turns with the partner protecting the nest site or offspring, and timing constraints change once the breeding season is over. Combined geolocator-immersion devices were deployed on eleven Imperial Shags (four males and seven females) in Argentina (43°04′S; 64°2′W) in November 2006 and recovered in November 2007. During the breeding season, females foraged throughout the morning, males exclusively in the afternoon, and variability between individuals was low. Outside the breeding season, both sexes foraged throughout the day, and variability between individuals was high. Timing differences may be explained by higher constraints on foraging or greater demands of parental duties experienced by the smaller sex, females in this case. Sexual differences in reproductive role, feeding habits or proficiency can also lead to segregation in timing of foraging, particularly while breeding. [ABSTRACT FROM AUTHOR]

Knowledge about interactions between endangered native southern river otters ( Lontra provocax) and introduced American mink ( Neovison vison) is essential for effective management of both species. We evaluated competition for spatial and trophic niches between otter and mink in overlapping and non-overlapping areas, comparing distribution, habitat preference, diet and mink marking behavior. We surveyed otter and mink signs along 250 km of Beagle Channel coastline. Habitat suitability models were constructed based on species presence/absence and habitat characteristics, using generalized linear models. Feces were collected for diet analyses. Otters used forested coasts with 12°-32° shoreline slope and without human influence, and our evidence suggests they were not affected by mink presence. Mink preferred forested and shrubland coasts with 10°-28° shoreline slope. Neither human influence nor otter presence affected mink habitat occupation, but in the presence of otters, mink left fewer signs. Otters consumed more aquatic prey than mink, and mink modified their diet in the presence of otters, consuming more exotic small terrestrial mammals and less fish as well as shifting to smaller and shallower fish species that are less consumed by otters. Mink showed more plastic, generalist behavior than otters, being more tolerant of human presence, using more habitat types and having greater diet breadth. At the same time, otters apparently affect mink adversely and could help limit their invasion in sympatric areas. Conservation and recovery of otters, therefore, may produce a secondary benefit of simultaneously reducing the effect of mink, thereby providing an additional way to control this exotic predator's population. [ABSTRACT FROM AUTHOR]

Abstract: The American mink (Neovison vison) is a semi-aquatic, generalist carnivore released onto Tierra del Fuego (TDF) Island in the 1940s, subsequently spreading to adjacent islands in the archipelago with potential effects on native prey populations. Knowledge of this new predator''s trophic ecology is essential to identify threats, plan control strategies and conserve native fauna. We studied seasonal mink diet in TDF in different habitats. We identified undigested remains from 493 scats collected between May 2005 and March 2009 along marine coasts and freshwater shores (rivers and lakes). Small mammals and fish were the main mink prey in TDF (over 65% of diet items). Seasonal variations were not detected, but diet did vary significantly between marine and freshwater habitats, where more terrestrial items were consumed. Among mammals, mink consumed more small native rodents than exotic species. Native fish consumption was also important with greater representation of species from the families Nototheniidae and Galaxiidae in marine and freshwater habitats respectively. Birds were the third item in importance, but did not constitute a particularly large part of the mink''s diet on TDF. Overall, differences found in mink diet between habitats reflected their generalist/opportunistic feeding behaviour and did not differ greatly from observations in its native range or in other areas where it has been introduced. Our results establish the interactions between this novel predator and its prey and also illustrate the need to continue research on native prey populations to quantify mink impact on them and understand the ecological context of this biotic assemblage. [Copyright &y& Elsevier]

The hourglass dolphin, Lagenorhynchus cruciger, is one of the smallest cetaceans found in Antarctic waters. Although frequently observed, this is one of the least studied species of dolphin. In this study, we investigate the occurrence of hourglass dolphin in the South-West Atlantic and Southern Ocean from 42°S to 63°S and characterize the oceanographic and environmental features associated with their occurrence. Sighting data were collected during two scientific cruises in December 2009 and January and February 2011 and integrated into a geographical information system with environmental variables such as sea surface temperature, ocean colour, depth, distance to oceanographic fronts and distance from shore. We used a principal component analysis (PCA) to identify patterns in data and a non-hierarchic cluster analysis ( K means) to classify observations into groups. A total of 19 sightings (96 individuals) were recorded. Group size ranged from one to twelve dolphins (mean 5.05). We could differentiate two groups in relation to the environmental conditions where animals were found, one group occurring in shallow coastal waters and the other occurring in deeper and colder waters further offshore. The present study contributes novel information on environmental measures associated with hourglass dolphin distribution in the South-West Atlantic and Southern Oceans. Additionally, it includes relatively high sighting clusters of this species in two highly productive and biodiverse areas (Burdwood Bank/Isla de los Estados and the South Shetland Islands). [ABSTRACT FROM AUTHOR]

The present article is the first formal record of pelagic swarms and beach strandings of the squat lobster Munida gregaria in the Beagle Channel, southern South America. To describe size composition and natural diet of beach strandings and swarms, samples from strandings were taken in April 2007, March 2008 and March 2010. Samples from swarms were taken in May 2007 and April 2010. Also, during November 2008 and January 2009, two acoustic surveys were carried out to describe both, horizontal distribution and school metrics of swarms. Pelagic swarms and beach strandings were composed of 100% individuals of the morph gregaria of M. gregaria. Mean size of males and females in both, beach strandings and swarms, were similar. The diet of pelagic M. gregaria was composed mainly of crustaceans, unicellular algae and small macroalgae, sediment and particulate organic matter. Swarms of pelagic Munida took the shape of extended layers of varying density and height. Their positions in the water column were also variable: swarms were found at different depths, from the subsurface layer to near the sea bottom. Occasionally, some large swarms occupied most of the water column. In the Beagle Channel, SW winds during spring tides could be a forcing factor for M. gregaria strandings. The absence of shoaling animals in the Beagle Channel between 1997 and 2002 and the recent occurrence of swarms are coincident with their appearance in other locations in Patagonia. In consequence, we hypothesize that the factor influencing the formation of swarms must be acting at a regional scale. [ABSTRACT FROM AUTHOR]

We examined the isotopic signatures (δC, δN) of adult body feathers from southern giant petrels Macronectes giganteus collected at two breeding colonies in Antarctica (Potter Peninsula and Cape Geddes) and one in southern Patagonia (Observatorio Island), as well as in whole blood collected from adults of both sexes at each Antarctic colonies and from chicks at Potter Peninsula. As body feather moult is a continuous process in giant petrels, feathers provide an integrated annual signal of an adult's diets and foraging habitats. In contrast, the stable isotope values of adult and chick blood are reflective of their diets during the breeding season. We found that sex-specific dietary segregation in adults breeding in Antarctica was notable during the breeding season (blood samples) but absent when examined across the entire year (feather samples). In addition, blood stable isotope values differed between chicks and adults, indicating that adults provision their offspring with a relatively higher amount of penguin and seal prey that what they consume themselves. This finding confirms previous work that suggests that chicks are preferentially fed with prey of presumably higher nutritional value such as carrion. Finally, based on isotopic differences between major oceanographic zones in the Southern Ocean, our data indicate population-specific differences in foraging distribution, with Antarctic populations move seasonally between Antarctic and subantarctic zones, while Patagonian populations likely forage in subtropical waters and in continental shelf habitats year-round. [ABSTRACT FROM AUTHOR]

Predation by fur seals and sea lions has been identified, among others, as a potential cause of the declines in rockhopper penguin populations. Here, we report a multiple predation event of southern rockhopper penguins Eudyptes chrysocome by South American sub-adult male sea lions Otaria flavescens at Staten Island, Argentina. The sea lions attacked and preyed on penguins mostly using a wait and rush tactic at sea, but in some cases, penguins were also pursued on land. Although observations suggested that only a few sea lions are involved in predation, further research is necessary to elucidate the importance of this predation in the rate of population decline. [ABSTRACT FROM AUTHOR]

This study investigates the movements of Magellanic Penguins Spheniscus magellanicus breeding on Isla Martillo during the early chick-rearing period. Foraging paths were reconstructed using GPS loggers that registered the penguins′ geographic position, water temperature and depth at regular intervals. The relationship between penguins′ movements and search strategies, tide and tidal currents were assessed. Mean trip duration was on average 14.7 ± 6.9 h (33% overnight), and the maximum distance reached was 24 ± 10 km. All penguins studied foraged to the east of the colony. We identified three phases based on the sinuosity and speed of the trajectory: transit, central and return. Foraging effort was higher during the central phase, followed by the transit phase, and lower in the return phase. Foraging success, measured as the percentage of time at the bottom during each phase, was also highest during the central phase. In all birds studied, the central phase of the foraging trip took place during ebb tide, and birds travelled to the foraging areas with flow tide running in the same direction of displacement. Our study suggests that penguins take advantage of tidal currents to facilitate their movements to and from the main foraging area, thereby reducing the energy expended. Moreover, we suggest that piscivorous diving birds may enhance their catch rate during ebb tide when fish are more concentrated near the channel bed. [ABSTRACT FROM AUTHOR]