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First published online August 25, 2003

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The integration of energy and nitrogen balance in the hummingbird Sephanoides sephaniodes

M. Victoria López-Calleja, María José Fernández and Francisco Bozinovic^*

Center for Advanced Studies in Ecology & Biodiversity and Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 651-3677, Chile

View larger version (19K): [in a new window]   Fig. 1. Body mass Mb change of green-backed firecrowns Sephanoides sephaniodes, fed diets with different nitrogen contents (see text) over a 10 day acclimation period. Mb of N-0 group changed significantly after treatment. Mb was significantly different between groups at the end of the acclimation period. Different letters indicate significant differences between groups after an a post-hoc Tukey test. The dotted line represents no change in body mass.

View larger version (16K): [in a new window]   Fig. 2. (A) Body mass Mb change and (B) nitrogen assimilation Ni by Sephanoides sephaniodes on experimental diets with different concentrations of nitrogen and on a natural diet with ad libitum N-0 nectar and fruit flies (Nect+FF). Values are means ± S.E.M. Different letters indicate significant differences between groups after a post-hoc Tukey test.

View larger version (15K): [in a new window]   Fig. 3. Apparent nitrogen retention of green-backed firecrowns Sephanoides sephaniodes fed on different experimental diets containing different nitrogen concentrations (see text). Regression equation is y=-1.19+59.16x/(69.22+x), r2=0.96, P<0.001. Nitrogen balance (or minimum maintenance nitrogen requirement, MNR, when y=0), occurs at an intake of 1.42 mg N d-1.

View larger version (16K): [in a new window]   Fig. 4. Linear regression of digestible energy intake (DEi) against overall change in the Mb of Sephanoides sephaniodes during 10-day feeding trials on diets of different nitrogen concentrations (see text). Regression equation is y=0.05x-2.15, r2=0.78, P<0.05. The DEi (44.0±1.1 kJ day-1) and Mb (-0.06±1.1 g), observed in birds fed the fruit flies and nectar diet ad libitum is indicated by the dotted lines.