Examinando por Autor "Zavalaga, C."
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Ítem Acceso Abierto Contaminants in tracked seabirds showing regional patterns of marine pollution(2013) Ito, A.; Yamashita, R.; Takada, H.; Yamamoto, T.; Shiomi, K.; Zavalaga, C.; Abe T.; Watanabe S.; Yamamoto, M.; Sato K.; Kohno H.; Yoda, K.; Iida T.; Watanuki Y.Ocean-scale monitoring of pollution is challenging. Seabirds are useful indicators because they travel over a broad foraging range. Nevertheless, this coarse spatial resolution is not fine enough to discriminate pollution in a finer scale. Previous studies have demonstrated that pollution levels are higher in the Sea of Japan and South and East China Seas than the Northen Pacific Ocean. To test these findings in a wide-ranging animal, we tracked streaked shearwaters (Calonectris leucomelas) from four islands in Japan using global positioning system (GPS) and measured persistent organic pollutants (POPs) in the oil of their preen glands. The POPs did not change during 6 to 21 days when birds from Awashima were foraging only in the Sea of Japan, while it increased when they crossed to the Pacific through the Tsugaru Strait and foraged along the eastern coast of Hokkaido where industrial cities occur. These results indicate that POPs in the oil reflect relatively short-term exposure. Concentrations of POPs displayed greater variation among regions. Total polychlorinated biphenyls were highest in birds foraging in a small area of the semiclosed Seto Inland Sea surrounded by urbanized coast, p,p″- dichlorodiphenyltrichloroethane (DDT) was highest in birds foraging in the East China Sea, and total hexachlorocyclohexanes were highest in birds foraging in the Sea of Japan. All were lowest in birds foraging in the Pacific. This distribution of POPs concentration partly agrees with previous findings based on mussels, fish, and seawater and possibly reflects the mobility and emission sources of each type of POP. These results highlight the importance of information on the foraging area of highly mobile top predators to make them more effective monitors of regional marine pollution. © 2013 American Chemical Society.Ítem Acceso Abierto Distribution and trends in kelp gull (Larus dominicanus) coastal breeding populations in South America(The Waterbird Society, 2016) Yorio, P.; Branco, J.O.; Lenzi, J.; Luna-Jorquera, G.; Zavalaga, C.In South America, Kelp Gulls (Larus dominicanus) breed from Chilean Tierra del Fuego north to Río de Janeiro, Brazil, on the Atlantic coast and to Piura, Peru, on the Pacific coast. This review presents the first synthesis of information on the distribution and size of Kelp Gull colonies at the country level in coastal environments of Uruguay, Chile and Peru; provides an update on the breeding situation of the species in Brazil and Argentina; and allows the first evaluation of the overall coastal breeding population in South America. The breeding population in South America is now estimated to number at least 160,000 pairs. The largest population (at least 106,000 breeding pairs) is found in Argentina. Colonies of more than 1,000 pairs are uncommon. Population trends differed among coastal sectors, and important increases in numbers and formation of new colonies were only observed in Argentina. Available information suggests that predictable and abundant anthropogenic food subsidies, such as fishery discards and urban waste, are key factors contributing to the population growth in some coastal sectors. There is no strong evidence that Kelp Gulls are currently expanding their breeding range. However, given the population expansion in some areas and the potential conflicts with humans, ongoing monitoring efforts and population evaluations are necessary as they will provide the information required to support management decisions.Ítem Acceso Abierto Selfies of imperial cormorants (Phalacrocorax atriceps): what is happening underwater?(Public Library of Science, 2015) Gómez-Laich, A.; Yoda, K.; Zavalaga, C.; Quintana, F.During the last few years, the development of animal-borne still cameras and video recorders has enabled researchers to observe what a wild animal sees in the field. In the present study, we deployed miniaturized video recorders to investigate the underwater foraging behavior of Imperial cormorants (Phalacrocorax atriceps). Video footage was obtained from 12 animals and 49 dives comprising a total of 8.1 h of foraging data. Video information revealed that Imperial cormorants are almost exclusively benthic feeders. While foraging along the seafloor, animals did not necessarily keep their body horizontal but inclined it downwards. The head of the instrumented animal was always visible in the videos and in the majority of the dives it was moved constantly forward and backward by extending and contracting the neck while travelling on the seafloor. Animals detected prey at very short distances, performed quick capture attempts and spent the majority of their time on the seafloor searching for prey. Cormorants foraged at three different sea bottom habitats and the way in which they searched for food differed between habitats. Dives were frequently performed under low luminosity levels suggesting that cormorants would locate prey with other sensory systems in addition to sight. Our video data support the idea that Imperial cormorants' efficient hunting involves the use of specialized foraging techniques to compensate for their poor underwater vision. Copyright: © 2015 Gómez-Laich et al.Ítem Acceso Abierto Strong temporal consistency in the individual foraging behaviour of Imperial Shags Phalacrocorax atriceps(Blackwell Publishing Ltd, 2014) Harris, S.; Raya Rey, A.; Zavalaga, C.; Quintana, F.Individual consistency in foraging behaviour can generate behavioural variability within populations and may, ultimately, lead to species diversification. However, individual-based long-term behavioural studies are particularly scarce in seabird species. Between 2008 and 2011, breeding Imperial Shags Phalacrocorax atriceps at the Punta León colony, Argentina, were tracked with GPS devices to evaluate behavioural consistency during their foraging trips. Within a breeding season, individuals were highly consistent in the maximum distances they reached from the shore and the colony, as well as in the time invested in flight and diving across consecutive days during early chick rearing. In addition, each individual had its specific foraging area distinct from the foraging area of other individuals. Comparing between early and late chick rearing in the same season, individuals were consistent, to a lesser degree, in the maximum distance they reached from the colony and the shore, increasing in consistency later on in the season. Within the season, females were more consistent than males in the maximum distance they moved from the colony and the shore, the sexes segregated in their foraging areas and individual females were segregated from one another. Twenty-eight individuals tracked in different breeding seasons were marginally consistent in their trip durations and maximum distance reached from shore across seasons. Among seasons, foraging locations differed between sexes and among individual females. Individuals from this colony exhibited consistency over time in several aspects of foraging behaviour, which may be due to a combination of individual characteristics such as learning abilities, breeding experience or health, as well as targeted prey type and stability of the environment at this location. © 2014 British Ornithologists' Union.