DOES LOSS OF MASS DURING BREEDING CORRELATE WITH REPRODUCTIVE SUCCESS- A STUDY ON BLUE TITS PARUS-CAERULEUS

Substantial loss of mass of female Blue Tits Parus caeruleus during br eeding is commonly explained by three not mutually exclusive explanati ons: shrinking of gonadal tissues, cost of reproduction and adaptation to save energy during night, This study showed that loss of body mass was inversely correlated with reproductive success of individual fema les, Female tarsus length and timing of breeding correlated with loss of body mass, whereas ectoparasite loading had no significant effect o n body mass, Loss of body mass during the rearing of young could be a useful measure of cost of reproduction by accounting for individual va riation in female quality.