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.
Animals facing seasonal food shortage and habitat degradation may adjust their foraging behaviour to reduce intraspecific competition. In the harsh environment of the world's southernmost forests in the Magellanic sub‐Antarctic ecoregion in Chile, we studied intersexual foraging differences in the largest South American woodpecker species, the Magellanic Woodpecker (Campephilus magellanicus). We assessed whether niche overlap between males and females decrease when food resources are less abundant or accessible, that is, during winter and in secondary forests, compared to summer and in old‐growth forests, respectively. We analysed 421 foraging microhabitat observations from six males and six females during 2011 and 2012. As predicted, the amount of niche overlap between males and females decreased during winter, when provisioning is more difficult. During winter, males and females (i) used trees with different diameter at breast height (DBH); (ii) fed in trunk sections with different diameters; and (iii) fed at different heights on tree trunks or branches. Vertical niche partitioning between sexes was found in both old‐growth and secondary forests. Such a niche partitioning during winter may be a seasonal strategy to avoid competition between sexes when prey resources are less abundant or accessible. Our results suggest that the conservation of this forest specialist, dimorphic and charismatic woodpecker species requires considering differences in habitat use between males and females.
Agonistic behavior in woodpeckers has been described for a wide range of species, although previous studies have not reported aggressive encounters resulting in the death of adults. In this study, we provide the first evidence of lethal agonistic behavior between two male Magellanic Woodpeckers (Campephilus magellanicus) inhabiting Patagonia. This species is commonly regarded as the largest extant Campephilus woodpecker. The agonistic encounter was video recorded within the core territory of the dead individual and his mate, a previously banded and monitored pair, as part of a monitoring research on this species carried out during the last 2 years. A week after the fight, we recorded a non-banded young male Magellanic Woodpecker accompanying the dead individual's mate. This young male Magellanic Woodpecker is potentially the offspring of the former pair or perhaps a new mate replacing the dead individual. From this observation, we deduced that the previously occupied territory of the dead individual, as well as its breeding role, was subjected to reallocation by competing adjacent woodpecker families. This mortality event offers novel insight into the behavior of Magellanic Woodpeckers and suggests that lethal agonistic behavior likely could contribute to territory plasticity and family structure in this species.
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