MULTI-SCALE INFLUENCE OF HABITAT AND DISTURBANCE ON THE SPATIAL ECOLOGY OF MAGELLANIC WOODPECKERS (CAMPEPHILUS MAGELLANICUS)
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Soto Gonzalez, Gerardo Emanuel
Habitat loss, fragmentation and degradation are major threats to biodiversity, yet landscapes can be managed in ways that reduce and/or mitigate the severity of such threats. Effective landscape management, however, requires a sound understanding of ecological responses to environmental gradients, human activities, and spatial configuration of habitats elements. A large body of research has established that species perceive, select, and respond to habitat across a hierarchy of spatial scales – from foraging substrates and micro-habitats to entire landscapes – as well as through a variety of coarse-grained and fine-grained processes. Although these processes are poorly understood in many systems, we urgently need to improve our knowledge in highly threatened places like the Valdivian Rainforest ecoregion, a global biodiversity hotspot within the South American temperate forests (SATF) of Chile. Conversion of forest to agriculture and pasture has left only 30% of the original Valdivian Rainforests, with forest remnants increasingly degraded by wildfires, unsustainable logging, and firewood extraction. This dissertation examined how Magellanic woodpeckers (Campephilus magellanicus), the primary cavity excavator of these forests, responded to habitat quality and quantity, social interactions, and landscape composition and configuration. Our specific objectives were to (1) innovate a remote-sensing method to estimate quality of foraging habitat; (2) investigate how nesting and roosting cavities affected within-territory habitat use; (3) understand the implications of foraging behavior and social interactions on seed dispersal; and (4) estimate the differential contributions of historic deforestation and exotic plantations on genetic population structure. We studied four populations of Magellanic woodpeckers from 2014 to 2017, employing multiple field and computational techniques including remote-sensing, satellite telemetry, surveys of birds, behavioral observations, inventories of cavities or other signs, and spatially-explicit models. We found that decay of Nothofagaceae trees, which is both an important component and indicator of habitat quality for Magellanic woodpeckers, was highly correlated with and estimable from remotely-sensed Plant Senescence Reflectance Index. Although tree decay can profoundly affect quality and use of foraging resources, we found that space use within territories was best explained by the abundance and distribution of previously-excavated cavities for nesting or roosting. In addition, territory size declined with proximity to neighboring families and increased with non-forest cover within individual territories. Our findings also show that both the drivers and consequences of space use were partly determined by social interactions among family members. For example, displacement by adult males expanded the ecological roles of females and juveniles to include seed dispersal across much larger distances than other known dispersers in our study system. The capacity of the species to move over large distances was confirmed, in part, by the low level of genetic differentiation among Northern populations. Nevertheless, we found no evidence that current movement constraints had yet scaled up to affect population structure, which was best explained by historic deforestation. Overall, our research provides the following insights into the consequences of Patagonian forest loss, degradation, and fragmentation on Magellanic woodpeckers: (1) the quality of foraging resources may be estimated by remote sensing, (2) legacy cavities (i.e., previously excavated) are overlooked but important resources that affect space use and territoriality, (3) social interactions can mediate the delivery of ecosystem services via seed dispersal, and (4) exotic plantations represent a novel barrier to movements that may have long-term consequences for population structure.
campephilus magellanicus; exotic plantations; forest degradation; magellanic woodpecker; space use
Rodewald, Amanda D.
Fuller, Angela K.; Royle, Andy; Dhondt, André
Ph. D., Natural Resources
Doctor of Philosophy
Attribution-NoDerivatives 4.0 International
dissertation or thesis
Except where otherwise noted, this item's license is described as Attribution-NoDerivatives 4.0 International