ornamental traits, female body size, and temperature
As female body size is correlated with female fecundity, larger females
of both Kentish plover and white-faced plover tended to have larger egg
sizes , which suggested a positive effect on offspring survival rate and
fitness . In accordance with sexual selection theory, which suggests
that more fecund females should mate with males with more elaborate
ornaments, we investigated the effects of male ornament PC1 and PC2
values, male body size, ambient temperature, and their interactions on
female body size
using
phylogenetic generalized linear mixed models (PGLMMs). In addition, we
included laying date and incubation period as fixed effects, while
population and year were included as random effects.
2.8
Modelling theeffect
ofmale
ornamental traits and temperature on parental investment during
incubation
We
classified incubation behavior as either female attendance, male
attendance, or absence of both parents at the nest. Due to instances of
nest predation, abandonment, or camera malfunctions, we only
analyzed
data from 71 nests with continuous recordings exceeding 24 hours. We
first tested the effect of ambient temperature on total incubation time
for each nest using a PGLMM. To control for the effect of ambient
temperature on total incubation time (see results), we calculated the
average daily incubation attendance of both parents and used the ratio
of an individual parent’s attendance to the total incubation time as a
measure of their investment. To investigate the effect of male and
female ornamental traits, body size, and temperature on parental
investment, we employed PGLMMs. Fixed factors included temperature and
the interaction between temperature and individual traits (if
significant).