|
|
|
|||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
First published online May 21, 2007
Journal of Experimental Biology 210, 2006-2012 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.001420
Metabolic rate of nocturnal incubation in female great tits, Parus major, in relation to clutch size measured in a natural environment
Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
* Author for correspondence (e-mail: m.e.de.heij{at}rug.nl)
Accepted 13 March 2007
To study the energetic costs of incubation in relation to clutch size, clutch sizes were manipulated and the metabolic rate of female great tits, Parus major (Linnaeus), during nocturnal incubation (MRinc) was measured using mobile oxygen analysers. Individuals were measured on consecutive nights while incubating their own or manipulated clutches. The experiment was performed under field conditions in order to place possible effects of clutch size manipulation within the context of other factors explaining variation in MRinc. Females spent more energy when incubating enlarged clutches as compared with controls (610% more energy for three additional eggs) but did not spend significantly less energy when incubating reduced clutches. MRinc was strongly negatively related to ambient temperature. The effect of clutch enlargement is consistent with previous studies whereas the absence of an effect of clutch reduction is not. The small effect of clutch enlargement on MRinc highlights the need for further studies to include measurements of daily energy expenditure in order to judge how important energy expenditure can be in explaining fitness consequences of incubating experimentally enlarged clutches.
Key words: clutch size manipulation, energy expenditure, natural selection, oxygen consumption