First published online August 25, 2003
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

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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.
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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.
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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.
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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.
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© The Company of Biologists Ltd 2003