Condition dependence, multiple sexual signals, and immunocompetence in peacocks

Condition-dependent expression of secondary sexual characters and measures of immune function in a cohort of similarly aged male blue peafowl Pavo cristatus was used to test whether different sexual signals provide information about different aspects of phenotypic quality. A measure of cell-mediated immunity and the heterophil--lymphocyte ratio demonstrated condition dependence, but a measure of humoral immunity was not condition dependent. Only train length demonstrated condition-dependent expression, while the number and the size of ocelli in the train did not show significant condition dependence. Although residual train length (after controlling for the number and the size of ocelli in the train) reliably reflected the magnitude of two condition-dependent measures of immunocompetence (positively with cell-mediated immunity and negatively with humoral immunity), residual size of ocelli was negatively related to cell-mediated immunity. Different features of the complex train were related in different ways to measures of immunocompetence. Copyright 2002.