Altitudinal variation in parental energy expenditure by white-crowned sparrows
Wesley W. Weathers1,2,*,
Charisse L. Davidson1,
Christopher R. Olson3,
Martin L. Morton4,
Nadav Nur3 and
Thomas R. Famula2
1 Department of Avian Sciences, University of California, Davis, CA 95616,
USA
2 Department of Animal Science, University of California, Davis, CA 95616,
USA
3 Point Reyes Bird Observatory, Stinson Beach, CA 94970, USA
4 Biology Department, Occidental College, Los Angeles, CA 90041,
USA

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Fig. 1. Mean wind speed (A) at the montane (dashed line) and sea-level (solid line)
study sites during measurements of daily energy expenditure. Mean air
temperature (B) at the montane (dot-dashed line) and sea-level (solid line)
sites and mean standard operative temperature at the montane (dotted line) and
sea-level (dashed line) sites. Means were determined from measurements made at
10- or 30-min intervals over 31 days at Tioga Pass Meadow (TPM) and 22 days at
Point Reyes Bird Observatory (PRBO).
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Fig. 2. Physiological variables of white-crowned sparrows during the incubation
(INC) and feeding nestling (FN) breeding stages for the montane (TPM) and
sea-level (PRBO) populations. Within variables, columns sharing the same
letter are not significantly different.
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Fig. 3. Relationship between daily energy expenditure and standard operative
temperature measured 1 m above ground in the open during the incubation
(shaded symbols) and feeding nestling (open symbols) breeding stages for
montane (triangles) and sea-level (circles) sparrow populations. BMR, basal
metabolic rate.
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Fig. 4. Relationship between resting, fasted rate of O2 consumption
(resting metabolic rate) and ambient temperature for montane (open circles)
and sea-level (shaded circles) white-crowned sparrow populations. See text for
details of the slopes.
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© The Company of Biologists Ltd 2002