From Tree-cavity to Landscape: Habitat Preferences and Fitness Operates Across Scales for an Old Relict Species of Southern South-america

Animals select their habitats from available resources in a way that should maximize fitness, and thus habitat preferences are generally predicted to be adaptive. However, there may be a mismatch between habitat preferences and fitness due to factors such as limited availability or disturbance of breeding habitats. In this study, we examine whether preferred nesting habitat attributes are linked to fitness (nesting success and number of fledglings) of White-throated treerunner ( Pygarrhichas albogularis ), an obligate excavator and tree cavity nester across four spatial scales: (1) cavity, (2) nest-tree, (3) forest-stand, and (4) landscape. During eight breeding seasons (October to February), between 2010 and 2018, we found and monitored 65 treerunner nests in Andean Temperate Forests, Chile. Our results show a multiscale response for both habitat preferences and fitness: both nest-tree and landscape scales were the most influential variables for nesting habitat preferences, while all habitat scales influenced fitness. The probability that a given habitat is used for nesting increased with larger trees, advanced tree decay classes, and forest cover. Nesting success was positively related with cavity entrance diameter, height, and distance from the forest edge. On the other hand, the number of fledglings decrease with larger trees and increase with decay class. Our findings suggest a match between habitat preferences and fitness. Finally, treerunners prefer areas with a relatively high forest cover and their nesting success increased with relatively lower tree density, suggesting that old-growth forests comprise the best integration of multiscale habitat attributes for this species.