TY - JOUR
T1 - Great tits provided with ad libitum food lay larger eggs when exposed to colder temperatures
AU - Schaper, S.V.
AU - Visser, M.E.
N1 - Reporting year: 2013
Metis note: 5399;Wag; AnE;
Data archiving: data archived at MDA
PY - 2013
Y1 - 2013
N2 - The amount of nutrients deposited into a bird egg varies both between and within clutches of the same female. Larger
eggs enhance offspring traits, but as a tradeoff, laying large eggs also infers energetic costs to the female. Income breeders
usually lay larger eggs later in the season, when temperatures and food availability are higher. Egg size is thus affected
by the daily amount of energy available to produce an egg under cold conditions, but it is less well known in how far
temperature exerts direct effects on egg size. We show that great tit females Parus major with access to ad libitum food
and breeding in climate-controlled aviaries varied their egg investments. The size of an individual egg was best predicted
by mean temperatures one week pre-laying, with females laying larger, rather than smaller, eggs under colder conditions.
Eggs increased in size over the season, but not significantly over the laying sequence. The degree of daily temperature
fluctuation did not influence egg size. In addition to a substantial between-female variation, sisters were more similar to
each other than unrelated females, showing that egg size does also reflect heritable intrinsic female properties. Natural
variation in egg size is thus not only determined by energy-limitation, but also due to females allocating more resources
to eggs laid in colder environments, thus increasing early survival of the chicks. That the positive correlation between
temperature and egg investments that is found in a natural population is reversed under ad libitum food conditions
demonstrates that wild great tits tradeoff own condition with survival prospects of their chicks as a function of available
food, not ambient temperature.
AB - The amount of nutrients deposited into a bird egg varies both between and within clutches of the same female. Larger
eggs enhance offspring traits, but as a tradeoff, laying large eggs also infers energetic costs to the female. Income breeders
usually lay larger eggs later in the season, when temperatures and food availability are higher. Egg size is thus affected
by the daily amount of energy available to produce an egg under cold conditions, but it is less well known in how far
temperature exerts direct effects on egg size. We show that great tit females Parus major with access to ad libitum food
and breeding in climate-controlled aviaries varied their egg investments. The size of an individual egg was best predicted
by mean temperatures one week pre-laying, with females laying larger, rather than smaller, eggs under colder conditions.
Eggs increased in size over the season, but not significantly over the laying sequence. The degree of daily temperature
fluctuation did not influence egg size. In addition to a substantial between-female variation, sisters were more similar to
each other than unrelated females, showing that egg size does also reflect heritable intrinsic female properties. Natural
variation in egg size is thus not only determined by energy-limitation, but also due to females allocating more resources
to eggs laid in colder environments, thus increasing early survival of the chicks. That the positive correlation between
temperature and egg investments that is found in a natural population is reversed under ad libitum food conditions
demonstrates that wild great tits tradeoff own condition with survival prospects of their chicks as a function of available
food, not ambient temperature.
KW - NIOO
U2 - 10.1111/j.1600-048X.2012.00129.x
DO - 10.1111/j.1600-048X.2012.00129.x
M3 - Article
SN - 0908-8857
VL - 44
SP - 245
EP - 254
JO - Journal of Avian Biology
JF - Journal of Avian Biology
IS - 3
ER -