Area-restricted search in Magellanic Woodpeckers: importance of tree senescence, forest composition and open habitats

Abstract

Background Large woodpecker species with stable territories, specialized diets and narrow habitat choices, such as the Magellanic Woodpecker (Campephilus magellanicus), are expected to adjust their movements based on the distribution of available resources within territories. Thus, Magellanic Woodpeckers should concentrate foraging activity in areas of higher quality, a behavior consistent with the area-restricted search (ARS) behavior. Although previous studies have deepened the understanding of how Magellanic woodpeckers select habitats, the assessment of ARS behavior would contribute to the identification of feeding areas important for their conservation and habitats hindering their movement. Methods We addressed the independent effects of tree senescence, forest succession, stand composition and open habitats on the adoption of area-restricted search (ARS) behavior in Magellanic Woodpeckers in a heterogeneous landscape dominated by southern beech forest in southern South America. Using GPS relocations from 24 woodpeckers, we estimated the First-Passage Time (FPT), a measure of the time individuals remain in a given area, with longer FPT values indicating the adoption of an ARS behavior. We determined the effects of habitat variables on FPT using a methodological framework based on Linear Mixed Effect models and a randomization procedure intended to reduce spatial autocorrelation arising from consecutive circles whose areas tend to be overlapped along trajectories. Results Averaged model coefficients showed that woodpeckers spent less time in sites dominated by the Antarctic beech (Nothofagus antarctica) and partially covered by open habitats. Conversely, FPT increased in stands and home ranges where tree senescence was higher. Conclusions The adoption of the ARS behavior in Magellanic Woodpecker is explained by forest composition, avoidance of open habitats and tree senescence. Our results suggest the conservation of Magellanic Woodpeckers in heterogeneous landscapes involve retention of senescent trees and restoring open areas in order to reduce edge habitat.