T. Amundsen et al., EFFECTS OF EGG SIZE AND PARENTAL QUALITY ON EARLY NESTLING GROWTH - AN EXPERIMENT WITH THE ANTARCTIC PETREL, Journal of Animal Ecology, 65(5), 1996, pp. 545-555
1. A large number of studies have reported a positive relationship bet
ween the egg size of birds and the subsequent growth and/or survival o
f nestlings, but such effects may partly be due to confounding variabl
es, e.g. parental quality. In order to evaluate the potential effects
of egg size, and of parental quality, on early nestling growth in the
Antarctic petrel, we performed an experiment in which eggs of differen
t size were swapped between nests. 2. From a sample of 300 nests with
eggs of known size, we selected eggs belonging to the lower quartile (
small eggs), and those belonging to the upper quartile (large eggs), w
ith respect to volume. Half of the small eggs were exchanged with smal
l eggs from other nests, and the other half with large eggs. A similar
procedure was used for large eggs. Growth and survival of the nestlin
gs were recorded until 12 days old. 3. Hatching success was positively
related to egg size. 4. Egg size influenced nestling body mass until
the age of 3 days, and tarsus length was affected until 12 days old. H
owever, these effects were not due to an effect of egg size on growth
rates, but reflected instead the influence of egg size on hatchling si
ze. 5. In contrast to most previous studies, we found no effect of par
ental quality (as reflected in the size of own eggs) on foster nestlin
g size or growth until 12 days old. This could be because egg size doe
s not reliably reflect parental quality in the species, or because par
ental effects become evident only at later nestling stages. 6. We disc
uss why egg size variation is maintained in this and other species whe
re egg size influences parental fitness through the survival of eggs o
r nestlings.