Condition dependence, multiple sexual signals, and immunocompetence in peacocks

Condition-dependent expression of secondary sexual charactersand measures of immune function in a cohort of similarly agedmale blue peafowl Pavo cristatus was used to test whether differentsexual signals provide information about different aspectsof phenotypic quality. A measure of cell-mediated immunityand the heterophil—lymphocyte ratio demonstrated conditiondependence, but a measure of humoral immunity was not condition dependent. Only train length demonstrated condition-dependentexpression, while the number and the size of ocelli in thetrain did not show significant condition dependence. Althoughresidual train length (after controlling for the number andthe size of ocelli in the train) reliably reflected the magnitudeof 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-mediatedimmunity. Different features of the complex train were relatedin different ways to measures of immunocompetence.