Examinando por Autor "Luna-Jorquera, Guillermo"

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    At-sea abundance and distribution of skuas and jaegers (Charadriiformes: Stercorariidae) at coastal waters off central Chile
    (Sociedad de Biología de Chile, 2014) Simeone, Alejandro; Anguita, Cristóbal; Luna-Jorquera, Guillermo
    BACKGROUND: Skuas and jaegers (Charadriiformes: Stercorariidae) are seabirds breeding at moderate to high latitudes and some perform extensive post-breeding transequatorial migrations. Most species overwinter and perform significant portions of their migratory flyways along the Pacific coast of South America, but scant information is available on their at-sea ecology in this waters. Our aims in this study were to determine: 1) the timing of occurrence and fluctuations in abundance of skua and jaeger species, 2) their spatial distribution within the coastal zone and 3) at-sea behavior of birds, including flock size and interactions with other seabird species. RESULTS: Between July 2006 and October 2013, we conducted at-sea bird counts at Valparaiso Bay (33°S) in central Chile and confirmed the occurrence of Chilean skuas (Stercorarius chilensis), Brown skuas (S. antarcticus), and Parasitic jaegers (S. parasiticus). Parasitic jaegers are regular austral summer visitors (November to March), whereas Brown skuas occur in the area only in winter (July to October). Chilean skuas were regularly recorded year-round in the area with higher abundances between late winter and early spring (August to October). Brown and Chilean skuas where observed comparatively offshore, whereas Jaegers presented a more coastal distribution, probably associated to host presence. Chilean skuas kleptoparasitized similar-sized (shearwaters and fulmars) and larger seabird species (boobies), whereas jaegers chased only smaller coastal birds (gulls and terns). Brown skuas engaged in no kleptoparasitic behaviors. All three species were observed mostly as solitary individuals. CONCLUSIONS: Skuas and jaegers showed in general a marked seasonality in their occurrence and abundance (only Chilean skua occurs year-round) and use this area as a commuting and stopover zone within their extensive migratory flyway along the southeastern Pacific.
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    Uncovering population structure in the Humboldt penguin (Spheniscus humboldti) along the Pacific coast at South America
    (Public Library of Science, 2019-05) Dantas, Gisele P.M.; Oliveira, Larissa R.; Santos, Amanda M.; Flores, Mariana D.; De Melo, Daniella R.; Simeone, Alejandro; González-Acuña, Daniel; Luna-Jorquera, Guillermo; Le Bohec, Céline; Valdés-Velásquez, Armando; Cardeña, Marco; Morgante, João S.; Vianna, Juliana A.
    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. © 2019 Dantas et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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    Unusual coastal breeding in the desert-nesting Gray Gull (Leucophaeus modestus) in northern Chile
    (The Waterbird Society, 2016-03) Aguilar, Roberto; Simeone, Alejandro; Rottmann, Jürgen; Perucci, Marietta; Luna-Jorquera, Guillermo
    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 colo nies 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, en ergy 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 Niño years in response to reduced food supply. During El Niño 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 Niño 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 Niño years or if this becomes a regular behavior independent of oceanographic conditions. Received 7 April 2015, accepted 12 May 2015.