Comparative Population Bioenergetics of Three Insectivorous Passerines in a Deciduous Forest

Abstract

At all levels of organization from the individual to the ecosystem, energy resources play a diverse and profound role. The ways in which these resources are used by a species represent the results of natural selection and are expressed in the species' life history patterns and adaptations (King 1974). Therefore, analyses of energy budgets, especially among similar species occupying the same environment, provide a means for understanding the ecological and energetic consequences of different life history phenomena. In addition, determinations of energy utilization and budgeting within species populations are useful in quantifying certain aspects of bird community structure and dynamics (Wiens 1973, Holmes and Sturges 1975, Karr 1975). Over the last two decades, energy budgets have been developed for several bird species occupying a variety of habitats (Orians 1961, Odum et al. 1962, Kale 1965, Brenner 1968, Pinowski 1968, Norton 1973, Custer 1974). No studies prior to ours (Black 1975; this paper), however, have been conducted on the population bionenergetics of insectivorous forestdwelling passerines. In this study, which is part of a larger investigation of bird community dynamics and energetics in the Hubbard Brook Experimental Forest, New Hampshire, we investigated the magnitude and seasonal patterns of time and energy use by three species of passerine birds: the Red-eyed Vireo (Vireo olivaceus), the Least Flycatcher (Empidonax minimus), and the Black-throated Blue Warbler (Dendroica caerulescens). These abundant and characteristic species of northern hardwoods forests differ in habits such as