Open AccessFemale great tits Parus major do not increase their daily energy expenditure when incubating enlarged clutches
Author(s) -
De Heij Maaike E.,
Ubels Richard,
Henk Visser G.,
Tinbergen Joost M.
Publication year - 2008
Publication title -
journal of avian biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.022
H-Index - 76
eISSN - 1600-048X
pISSN - 0908-8857
DOI - 10.1111/j.2008.0908-8857.04286.x
Subject(s) - incubation , biology , parus , nest (protein structural motif) , energy expenditure , avian clutch size , clutch , zoology , offspring , attendance , ecology , endocrinology , reproduction , pregnancy , physics , thermodynamics , biochemistry , genetics , economic growth , economics
Several studies have shown that enlargement of clutches during incubation reduces the long‐term survival of parents. In line with these findings, studies on the energetic costs of nocturnal incubation show an increase in energy expenditure with clutch enlargement. Studies on daily energy expenditure during incubation (DEE inc ), however, do not consistently show such a negative effect of clutch enlargement. To determine whether differential survival results from a direct increase in energy costs or rather from costs associated with compensatory behaviour, we studied the DEE inc (kJ day −1 ), change in body mass and nest attendance behaviour of free‐living female great tits Parus major that incubated either control or experimentally enlarged clutches. DEE inc did not differ between the two treatment groups, but was negatively related to mean ambient temperature over the 24‐h measuring period, and to the fraction of daytime females spent on the nest. Controlling for these two factors, females incubating enlarged clutches did not spend more energy per 24 h period than females incubating control clutches. Clutch enlargement also did not affect body mass of incubating females, or their nest attendance behaviour. Yet, in the enlarged group body mass change and nest attentiveness were negatively correlated, suggesting that females responded differently to the experimental treatment and thereby preventing us from finding an effect of clutch enlargement.