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Summary: TheAuk 114(1):133, 1997
Is the EnergyCostof Beggingby Nestling PasserinesSurprisingly Low?
WESLEYW. WEATHERS,· PETERJ. HODUM, AND D^VlD J. ANDERSOl·I2
DepartmentofAvianSciences,UniversityofCalifornia,Davis,California95616,USA
McCarty (1996)reported that oxygenconsumption
rates(402)ofrestingandbeggingnestlingsoffive
passerinespecieswerelittledifferentandoftenequiv-
alent. From this he concludedthat beggingis not a
costly trait. In 1990, we obtained a similar result
(WeathersandAndersonunpubl.data)with nestling
ZebraFinches(Taeniopygiagutrata)usinga moresen-
sitive402 methodthanMcCarty's.Weplacednest-
ling Zebra Finchesin a small-volumerespirometer
(350 mL) and employed open circuit respirometry
coupled with the "instantaneous"method to deter-
mine402(Bartholomewetal.1981).Despitefinding
negligibledifferencesbetweenthe(tO2of begging
and restingnestlings(lessthan a 5% increaseover
resting levels;n = 3), we were unable to conclude
that begginghad a low energycostbecausewe mea-
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