Habitat loss and degradation on oceanic islands are key processes leading to population decline of endemic birds and facilitating the establishment of invasive bird species. In this study, carried out in the Robinson Crusoe Island, we assessed density and habitat selection of terrestrial bird species, including juan fernandez firecrown and juan fernandez tit-tyrant, two endemics, as well as green-backed firecrown and austral thrush, which apparently originate from the mainland. Results show that perturbed habitats contained a low density of the endemic species whereas the mainland species were significantly more abundant in perturbed scrub habitats. Bird species show different habitat selection patterns, with endemics selecting for native forest and mainland species selecting for perturbed habitats, or using them at random. Bird species experienced temporal trends in their overall population sizes, with the endemic tit-tyrant suffering a significant decline in its population size of about 63% between 1994 and 2009. Only mainland species exhibited temporal changes in habitat use, significantly reducing their densities in the preferred scrub habitats, possibly as a response to decreased habitat quality. Thrushes apparently were able to compensate the population decrease in one non native habitat type by using native forests, a habitat giving them the opportunity of preying on nests of endemic species. We conclude that endemic bird species behave as specialists whereas the mainland species must be treated as invasive generalists on Robinson Crusoe Island.

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The first nest sites of the endemic Ma´safuera Rayadito (Aphrastura masafuerae) are described, the first one being found on 16 December 1992. Ma´safuera Rayaditos breed in small natural holes in steep rocks, the nest being hidden within the rock and not visible through the 3 cm-wide entrance. All nest sites were located in the summit region of Alejandro Selkirk Island above 1,200 m altitude, characterised by fern stands. Nesting has been reported from early December to late January. Feeding frequency increases only slightly during nestling time. Both parents feed the nestlings in similar proportions. During the daily round no regular variation in feeding frequency occurs, although it is often higher during the first hours after sunrise. In general, it decreases strongly when a Ma´safuera Hawk (Buteo polyosoma exsul) is present close to the nest site. It hunts intensively on Rayaditos, both adults and juveniles. Habitat destruction and predation pressure have caused the Ma´safuera Rayadito to be the most endangered bird species in Chile (total population c. 140 individuals). More detailed studies on its breeding ecology are urgently needed, especially on reproductive success.

The abundance of woodland birds in fragmented forest landscapes may depend on the properties of patch networks. Understanding the consequences of deforestation on woodland birds, therefore, necessarily requires determining which changes in landscape structure make a major contribution to the degradation and subdivision of patch networks. In this study, we addressed how accelerated deforestation in central Chile has modified the landscape structure and function for thorn‐tailed rayaditos—a woodland specialist bird. Using a graphical approach based on the habitat use and movement patterns of rayaditos, we quantified the reduction of the internal connectivity of components (i.e., connected patch networks) in the last two decades and determined the main mechanisms responsible for this connectivity loss. Forest cover decreased 61.7 % between 1989 and 2009. The component size, the fraction of components with ≥1 occupied patches and the number of patches per component experienced a large decline during the study period. Over time, most forest cover (ca. 80 %) was contained in only two components. The connectivity of components decreased steeply by 90 %. Only the loss of large patches made a highly significant contribution to explaining changes in connectivity, while the removal of stepping stones was marginally significant. The conversion of forest both to shrubland and to peri‐urban areas were the only land‐use variables explaining connectivity change with effects that changed over time. Conservation measures to ensure persistence of rayaditos populations in central Chile should be focused on the retention of key elements for connectivity.

SUMMARYThe effect of the disturbances caused by the American beaver (Castor canadensis), introduced to the Cape Horn Biosphere Reserve, on species of birds that are forest habitat specialists is poorly understood. Using telemetry data, we determined which attributes of abandoned beaver meadows have a strong impact on habitat selection by the Magellanic woodpecker (Campephilus magellanicus). We detected a positive relationship between the woodpecker habitat use and the fraction of old-growth forest located near these meadows. These results suggest that favorable habitat conditions are generated around small meadows with old-growth forest, because they might increase availability of wood-boring larvae.Key words: American beaver, Campephilus, habitat selection. RESUMENEl efecto que tienen las perturbaciones causadas por el castor norteamericano (Castor canadensis) -introducido en la Reserva de Biosfera Cabo de Hornos-sobre especies de aves especialistas de hábitat forestales es poco conocido. Utilizando datos de telemetría determinamos qué atributos de las castoreras abandonadas tienen una mayor influencia en la selección del hábitat por los carpinteros negros (Campephilus magellanicus). Existe una asociación negativa entre el uso del hábitat por carpinteros y el tamaño de las castoreras, mientras que los carpinteros muestran preferencias por el bosque antiguo ubicado cerca de estas castoreras. Estos resultados sugieren condiciones de hábitat favorables cerca de las castoreras pequeñas y rodeadas de bosque antiguo, probablemente debido a un aumento en la disponibilidad de larvas taladradoras de madera.Palabras clave: Castor norteamericano, Campephilus, selección de hábitat.