Interpopulation resource partitioning of Lesser Frigatebirds and the influence of environmental context. Issue 23 (10th November 2016) - Mott, Rowan
Abstract: Conspecific individuals inhabiting nearby breeding colonies are expected to compete strongly for food resources owing to the constraints imposed by shared morphology, physiology, and behavior on foraging strategy. Consequently, colony‐specific foraging patterns that effectively partition the available resources may be displayed. This study aimed to determine whether intraspecific resource partitioning occurs in two nearby colonies of Lesser Frigatebirds ( Fregata ariel ). A combination of stable isotope analysis and GPS tracking was used to assess dietary and spatial partitioning of foraging resources during the 2013 and 2014 breeding seasons. These results were compared to vessel‐derived estimates of prey availability, local primary productivity, and estimates of reproductive output to suggest potential drivers and implications of any observed partitioning. Isotopic data indicated a more neritic source of provisioned resources for near‐fledged chicks at an inshore colony, whereas their offshore counterparts were provisioned with resources with a more pelagic signal. Deep pelagic waters (>200 m) had higher availability of a preferred prey type despite a trend for lower primary productivity. Differences in foraging ecology between the two populations may have contributed to markedly different reproductive outputs. These findings suggest environmental context influences dietary and spatial aspects of foraging ecology. Furthermore, the effect of colony‐specific foraging patterns on population demography warrants further research. Abstract : Intra‐specific competition can result in resource partitioning that minimises resource overlap. This study identified spatial and dietary partitioning in the foraging ecology of Lesser Frigatebirds ( Fregata ariel ) from two nearby colonies. Environmental context, in particular the availability of a preferred prey‐type, likely influences spatial and dietary aspects of foraging ecology and could contribute to colony‐specific differences in reproductive output.