Meeting Abstract
For birds overwintering in temperate regions, foraging is arguably one of the most important behaviors affecting fitness. While many factors influence foraging, few studies have addressed the relationship between behavior, energy constraints and its consequences on survival. We examined how the metabolic flexibility of individual Black-capped Chickadees (Poecile atricapillus) influenced their foraging response to temperature changes across a gradient of forest fragmentation. We predicted individuals with low metabolic flexibility would be more energetically constrained, forcing them to forage more under harsh winter conditions, and increasing costs of mortality due to the tradeoff between foraging intensity and predation risk. Lastly, we expected birds in fragmented landscapes would have higher metabolic flexibility due to greater selective pressures on birds with low metabolic flexibility. During winter 2014/15, we quantified foraging behaviors of birds at supplemental feeding stations using radiofrequency identification. We calculated metabolic scopes (summit – basal metabolic rate) for 28 birds as a snapshot of metabolic flexibility. Low scope birds were more energetically constrained and significantly increased their feeder visitation as temperatures declined over winter. These birds were 70% less likely to survive the winter compared to individuals with high metabolic scope. Lastly, birds in fragmented landscapes had 16% higher scope, suggesting greater selective pressures against more energetically constrained behavioral phenotypes. To our knowledge, this is the first study to examine the link between energy constraints and foraging on survival of birds in human-modified landscapes.
