4 DISCUSSION
We conducted a comprehensive analysis of the relationship between reproductive traits (body size and ornamentation) and female investment in incubation to demonstrate how ambient temperature modulates female pre- and post-copulatory mate choice preference in plover populations. The observed phenomenon could be attributed to the trade-off between ornamentation and body size in males in colder environments. Our findings revealed a positive association between male body mass and ornamentation in warmer regions and a negative correlation in colder habitats. Larger and more colorful females preferred more colorful males in warmer habitats, but this tendency was missing in colder conditions. Furthermore, in warmer conditions, colorful males engaged less in incubation, and path studies revealed that females compensated for the reduced degree of male parental care.
However, in colder environments, parental incubation only depended on ambient temperature. Our data consistently imply that ambient temperature influences plover mate selection.
4.1 Trade-off between ornaments and morphologicaltraits varies with ambient temperatures
Body size and mass are often employed as measurements of energy reserves and can somewhat reflect an individual’s condition or quality . Previous research has found a positive correlation between sexual signals and condition indices such as body size and body condition , with some exceptions . Condition indices are projected to trade-off against other life-history features, including sexual signals, as a life-history trait . We found evidence of a trade-off between colorful ornaments and body size in males in colder environments, suggesting that under harsh environmental conditions, male traits related to self-maintenance may be favored by natural selection . In contrast, under warmer environmental conditions where the total incubation requirement is lower and suggests a mild environment, males exhibited a positive relationship between body size and ornamental traits. The relationship between body size and ornaments with ambient temperature suggests that under harsher environments, individuals may need to allocate resources to body size due to life-history trade-offs.