No abstract

Anthropogenic Marine Debris (AMD) in the SE Pacific has primarily local origins from land-based sources, including cities (coastal and inland), beach-goers, aquaculture, and fisheries. The low frequency of AMD colonized by oceanic biota (bryozoans, lepadid barnacles) suggests that most litter items from coastal waters of the Humboldt Current System (HCS) are pulled offshore into the South Pacific Subtropical Gyre (SPSG). The highest densities of floating micro-and macroplastics are reported from the SPSG. An extensive survey of photographic records, unpublished data, conference proceedings, and published studies revealed interactions with plastics for 97 species in the SE Pacific, including 20 species of fish, 5 sea turtles, 53 seabirds, and 19 marine mammals. Sea turtles are most affected by interactions with plastics, underlined by the fact that 4 of the 5 species suffer both from entanglement and ingestion. Reports gathered in this review suggest that interactions along the continental coast are mostly via entanglement. High frequencies of microplastic ingestion have been reported from planktivorous fish and seabirds inhabiting the oceanic waters and islands exposed to high densities of microplastics concentrated by oceanic currents in the SPSG. Our review also suggests that some species from the highly productive HCS face the risk of negative interactions with AMD, because food and plastic litter are concentrated in coastal front systems. In order to improve the conservation of marine vertebrates, especially of sea turtles, urgent measures of plastic reduction are needed.

The Peruvian Booby (Sula variegata) is one of the most numerous guano bird species in the Humboldt Current. We used a combination of data logger deployment, at-sea observations and colony-based work to investigate the foraging and diving behaviour, as well as the at-sea distribution and food choice of Peruvian Boobies breeding at Isla Pajaros, northern central Chile. Birds foraged in the vicinity of Isla Pajaros. They performed short foraging trips, varying between a few minutes and several hours. Average foraging range was 17.1 ± 3.5 km and diving took place between 2 and 10 km off the coast. Birds dived to depth of up to 10 m with an average depth of 4.3 ± 1.5 m. By at-sea observations as well as by data logger deployment, we identified important foraging areas close to the coast, especially around protruding points. The birds' diet was highly variable between years, with Inka scad (Trachurus murphyi) and anchovy (Engraulis ringens) being the overall dominant prey species. Despite limited sample sizes, this paper presents first results about the foraging behaviour of Peruvian Boobies at the largest breeding colony in northern Chile. This information is essential for a better understanding of the effects of environmental changes as well as for the implementation of conservation measures.

. Birds feeding chicks need to balance the costs of either (1) returning to the breeding island for the night and travelling back to the feeding grounds in the morning or (2) incurring increased thermoregulatory costs associated with resting at sea overnight. Simple calculations show that at water temperatures of 19°C we expect Humboldt penguins to show a tendency to remain at sea overnight if foraging areas are > 4 km from their island. In colder waters (12°C), this distance increases to > 9 km. Using previously published data on at-sea activity of Humboldt penguins, we found that foraging costs during chick rearing amount to 340 g anchovies d -1 . Finally, we present a general model to convert Humboldt penguin activity data at sea to food requirements.

In less than one century, the once-abundant Peruvian diving petrel has become the first endangered seabird of the Humboldt Current System (HCS). This small endemic petrel of the South American Pacific coast is now an important indicator of ongoing habitat loss and of the success of local conservation policies in the HCS - an ecoregion designated as a priority for the conservation of global biodiversity. Yet so far, poorly understood life history traits such as philopatry or dispersal ability may strongly influence the species’ response to ecosystem changes, but also our capacity to assess and interpret this response. To address this question, we explore the range-wide population structure of the Peruvian diving petrel, and show that this small seabird exhibits extreme philopatric behavior at the island level. Mitochondrial DNA sequences and genome-wide SNP data reveal significant isolation and low migration at very short distances, and provide strong evidence for questioning the alleged recovery in the Peruvian and Chilean populations of this species. Importantly, the full demographic independence between colonies makes local population rescue through migration unlikely. As a consequence, the Peruvian diving petrel appears to be particularly vulnerable to ongoing anthropogenic pressure. By excluding immigration as a major factor of demographic recovery, our results highlight the unambiguously positive impact of local conservation measures on breeding populations; yet at the same time they also cast doubt on alleged range-wide positive population trends. Overall, the protection of independent breeding colonies, and not only of the species as a whole, remains a major element in the conservation strategy for endemic seabirds. Finally, we underline the importance of considering the philopatric behavior and demographic independence of breeding populations, even at very fine spatial scales, in spatial planning for marine coastal areas.

Oceanic marine protected areas (MPAs) that are close to the litter accumulation zones in the subtropical gyres receive large amounts of plastic litter, both as micro‐ and as macroplastics. The macro‐litter accumulating on the islands in the Easter Island Ecoregion (Rapa Nui and Salas y Gómez) can be traced back to the high seas industrial fishery operating in the South Pacific. Seabirds nesting in the MPAs in the South Pacific are affected by both microplastic ingestion and macroplastic in their nests, but there was no evidence of entangled birds. Conservation of seabirds (and other species) in these oceanic MPAs requires efficient measures to reduce plastic contamination in the ocean. Observations made in the South Pacific coincide with those from other oceanic MPAs, calling for global actions.

Marine ecosystems and their inhabitants are increasingly under threat from climate change, competition with humans for resources, and pollution. Species that are endemic to particular currents or regions of the world's oceans have the potential to be at higher risk due to localized overfishing, pollution, or locally severe impacts of climate change such as more intense, or longer, El Niño Southern Oscillation events. Understanding patterns of population differentiation in endemic marine organisms may be particularly important for their conservation and persistence. Peruvian Boobies (Sula variegata) are endemic to the Humboldt Current upwelling system and have experienced population fluctuations throughout their evolutionary history due to both dramatic reduction of food supplies, and anthropogenic influence over the last *150 years. Recent research on other members of the Sulidae indicates that populations of these primarily tropical seabirds show a high degree of genetic differentiation; however, the sister species of the Peruvian Booby, the Blue-footed Booby (S. nebouxii), exhibits only weak rangewide population genetic structure. We characterized population genetic differentiation and diversity in 153 Peruvian Boobies using sequence variation of 540 base pairs of the mitochondrial control region and seven microsatellite loci. Although we found evidence of panmixia, a signature of isolation by distance appears to exist between the five sampled colonies. We also found unexpectedly high genetic diversity given this species' recent population decline. Our results are similar to those for the Humboldt Penguin (Spheniscus humboldti), another endemic of the Humboldt Current upwelling system.

Anthropogenic impact has been heavy in remote oceanic islands, including the introduction of alien species, having negative effects on native seabirds. The isolated and subtropical Rapa Nui (Easter Island) is one of the few known breeding sites of the red-tailed tropicbird, Phaethon rubricauda in Chile (southeastern Pacific Ocean) where is listed as vulnerable. A relatively new breeding colony is found in the Rano Raraku volcano, where human-introduced species are present. We used hen eggs as a proxy for red-tailed tropicbird eggs to assess potential predation risk on unattended eggs. Each experimental egg was monitored by camera traps during 6 days. Three predatory species were identified on the records: the Brown rat Rattus norvegicus, the Polynesian rat Rattus exulans, and the raptor Chimango Caracara Phalcoboenus chimango. The most frequent species were the Rattus spp. A total of 45 predatory visits were recorded with a total time of 1.7 h, accounting for the 0.3% of the experimental time. Within this time of visits, all the potential predators spent time in both interacting activities (trying to prey on) and no-interacting activities with the experimental eggs. Only a Brown rat was able to prey on one of the eggs. Our results suggest that these invasive species are a low threat for unattended red-tailed tropicbird eggs at Rano Raraku, Rapa Nui. However, future research is needed to determine the potential negative effects over unattended red-tailed tropicbird nestlings that are easier for these predators to handle compared with an egg.