Gray gulls Larus modestus are unique among birds of northern Chile as the only species nesting in the interior Atacama Desert, and the only seagull nesting far (30 - 100 km) from surface water. During breeding-nesting (August - February) gray gulls congregate on the coast of northern Chile where they feed and initiate courtship. As early as August, breeding pairs commute daily to the inner desert to establish nesting territories, round-trip distances of 60-200 Km. During incubation (30 days) and brooding (7 days) adults alternate daily foraging flights to the coast. Afterwards, both adults forage daily for their chick(s) until fledging (ca. 60 days). Foraging flights and thermoregulatory costs during the period of maximal solar radiation, when ground temperatures may reach 61 C in the day and drop to 2 C at night, have selected for adaptations which minimize those costs: tolerance of hypothermia and hyperthermia; dark plumage; low egg-shell water vapor conductance; low standard metabolic rate; elaborate repertory of thermoregulatory behavior which allow adults to take advantage of microclimatic variations in the desert and minimize costs relative to a sympatric congenor, Larus belcheri scheduling foraging flights to take advantage of optimal atmospheric conditions and presence of forage fish (anchovies) close to the surface; scheduling migration to coincide with anchovy production and levels of interspecific competition; and reduced clutch size ( ≤ 2) relative to most seagulls. Periodic El Nino-Southern Oscillations (ENSO), which reduce principal food items of gray gulls, have selected for 'bet hedging" tactic by which L. modestus either ceases reproduction or varies clutch size between one and two, as observed during and after the 1982-83 ENSO. During a typical reproductive season, breeding pairs allocate a minimum of 39 percent of their net metabolized energy (NME) to foraging flights. Including energy content of eggs, females have an overall …
This study is an attempt to contribute to the emerging theoretical literature on state repression. A time-series model was developed to test the hypothesis that state violence in Argentina and Chile is largely a function of four internal political factors and their interactions: 1) the inertial influence of past restrictive policies on the formulation of current policies, 2) the annual incidence of political protest demonstrations, 3) the perceived effectiveness of repressive measures on unrest, 4) and the institutionalization of military rule.
General objectives of my study were to describe the reproductive ecology of gray gulls in the large Lealtad colony, with emphasis on demographic parameters and physiological adaptations of eggs and chicks, which would complete some original objectives established in the early 1980's by Guerra and Fitzpatrick. Specifically, my study focused on describing, then comparing with other desert and non-desert nesting larids, interactive effects of ambient physical conditions and nest-site predation on eggs and chicks.
The Cape Horn Biosphere Reserve is located at the southern tip of South America. This large archipelago is considered one of the last pristine areas left on the world. Despite it being an unpopulated area with most of the native forest cover intact, it has not been exempt from biological invasions, one of the major drivers of biodiversity loss. Three species that naturally interact in their native range in North America – American beavers (Castor canadensis), muskrats (Ondatra zibethicus), and American mink (Neovison vison) – were independently introduced in this remote region. In my dissertation, I investigated (i) the hypothesis of niche expansion in the invasive mink population on Navarino Island towards terrestrial habitats; (ii) potential mink impact on breeding success of forest-bird populations; (iii) habitat selection of small-rodent species and their perception on the mink's novel predation risk; and (iv) the dynamics of multiple-species invasions under the hypothesis of an invasional meltdown. Additionally, I worked within the framework of environmental philosophy. I provide an example of combining ecological and cultural dimensions within the International Long-Term Ecological Research network to disentangle the ethical dilemmas that surround the management of invasive species. I finally proposed a management plan based on the idea of multiple invasive species management, discussing potential solutions to overcome the challenges that the control of invasive species represent and to more effectively protect the biological integrity of the native ecosystems.
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