Effects of parental provisioning and attendance on growth and survival of red-throated Loon pre-fledglings: A potential mechanism linking marine regime shifts to population change

Since the 19701s, several piscivorous birds and marine mammals in Alaska have declined numerically, coincident with oceanic regime-shifts and associated prey community changes. Red-throated Loons have similarly declined and this study supports the hypothesis that impoverished prey conditions are a potential mechanism that could reduce productivity by altering chick growth and survival. During 2002-2003, moderate-to-low energy fishes dominated the prey community. This potentially constrained parental ability to meet brood attendance and energy requirements. Two-chick broods were not fed at higher rates than single-chick broods and all two-chick broods were reduced, apparently from starvation of the younger sibling. Energy consumption also influenced first-hatched chick survival during week one, when both provisioning effort and attendance requirements were high. For chicks surviving this early period, sex influenced growth variation more than energy consumption. Overall, survival and growth performance measures were poorer than published findings, suggesting poor foraging conditions were a mechanism limiting productivity.