Bioenergetics of Hawaiian Honeycreepers: the Amakihi (Loxops virens) and the Anianiau (L. parva)

Abstract

Insular biotas have attracted considerable biological attention, and have been very important in the formulation of evolutionary thought and theory. Since Charles Darwin's visit to the Galapagos Islands and his description of the Galapagos Finches, insular land birds have played very prominent roles in evolutionary biology, largely based upon detailed morphological and taxonomic analyses. Yet virtually no attention has been paid to assessments of the functional attributes of terrestrial birds inhabiting oceanic islands. Ideal candidates for studies of adaptive physiology of an island avifauna are the endemic Hawaiian Honeycreepers (Passeriformes: Drepanididae) which exhibit among their…. "numerous species the most striking example of adaptive radiation from an assumed single ancestral species of any bird family in the world" (Berger, 1970). This study undertakes to examine certain bioenergetic characteristics of two congeneric species of Hawaiian Honeycreepers, the Amakihi (Loxops virens) and the Anianiau (L. parva), with the view of providing data for comparisons with those derived from continental land birds. Such data, hopefully, will reveal the magnitudes of physiological divergence and/or convergence of these island birds. Included in this study are assessments of oxygen consumption, thermoregulation, and evaporative water loss.