Juvenile songbird movement and habitat use in harvested boreal forest landscapes of western Newfoundland.

摘要

Understanding the relationship between landscape structure and the distribution and movement of organisms is a central theme in the study of landscape ecology. Prior to migration, juvenile Neotropical migrant songbirds are energetically constrained due to foraging inefficiencies, predation risk, and increasingly inclement weather. Not being able to obtain adequate resources may result in mortality prior to or during migration, directly influencing population dynamics. Resource managers must identify productive habitat and ensure its accessibility. I investigated the adaptive significance of broad-scale movements, and the relationships between landscape composition (at multiple spatial extents) and movement rate/habitat associations for two closely related but ecologically distinct species of juvenile songbird in harvested boreal forests of western Newfoundland. Using radio telemetry, I followed the movement of juvenile yellow-rumped (Dendroica coronata; hereafter YRWA) and blackpoll warblers (D. striata; hereafter BLPW) over two postfledging periods, post-dependence, in 2005 and 2006. YRWAs made directed movements to low elevation habitat prior to migration. BLPWs made directed movements in an effort to form a homing target for return in the spring. Movement of both species was not impeded by harvested landcover at the extents investigated. YRWAs did not associate with harvested landcover, whereas BLPWs associated with harvested landcover at neighborhood and landscape extents. In summary, both species utilized the broad landscape for different purposes. Response in terms of movement and habitat association to harvested landcover at multiple spatial extents also varied by species. Further research is needed to relate observed movement patterns to fitness and to ensure that adequate resources are obtained.