POLYGYNY IN GREAT REED WARBLERS - A LONG-TERM STUDY OF FACTORS CONTRIBUTING TO MALE FITNESS

To study the relative importance of factors with direct and indirect e ffects on male fitness in the polygynous Great Reed Warbler, Acrocepha lus arundinaceus, I investigated characteristics of both males and ter ritories in relation to annual and lifetime breeding success. Male har em size and number of offspring recruits (i.e., young surviving to bre eding age) were repeatable between years. I analyzed lifetime breeding success using stepwise multiple regressions and annual breeding succe ss by testing for significant trends (over five years) in pairwise cor relations with each male and territory characteristic. Male arrival or der was the most important factor predicting pairing success, hedging success, and number of offspring recruits, and arrival order was also closely correlated with territory attractiveness rank. Thus females se emed to prefer early arriving males that occupied more attractive terr itories, and these females also gained direct benefits through increas ed production of fledglings and offspring recruits. Older males arrive d earlier and were therefore able to occupy attractive territories. Ma le song repertoire size was positively correlated with annual harem si ze and annual and lifetime production of offspring recruits. Song repe rtoire size alone predicted male lifetime number of offspring recruits statistically adjusted for number of fledglings produced, i.e., the p ostfledging survival of offspring. These data suggest that males with large song repertoires sire offspring that have improved viability, an d that females mating with these males can gain indirect (genetic) ben efits for their young.