The effects of male body size, age and gregarine parasite load on the structure of calls and success at attracting mates were investigated in a natural population of the field cricket, Gryllus bimaculatus. The syllable rate within chirps was negatively related to male size, and the duration of syllables was positively related to size. Older males had more variable syllable rates within their chirps. Size did not influence pairing success. However, paired males were significantly older than solitary calling males. Parasitic infection influenced the pairing success of young males but not old males. These data are discussed in the context of direct and indirect selection for female mating preferences.
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We are extremely grateful to the director of the Dofiana Biological Station, Miguel Delibes, for allowing us entry to the reserve and providing us with research facilities. We would not have survived without the help of Tomas Redondo and Fernando Alvarez. We thank John Rotenberry for help in the field, and Rana Bindra, Lynn Diaz and Nadeem Tusneem for help with the call analysis. Win Bailey, Dale Roberts and Ian Dadour gave valuable advice and comments on the original manuscript. This work was supported by an ASAB short project grant to L.W.S. and a Field Research Travel grant from UCR to M.Z.