PATERNITY AND MULTIPLE SIGNALING - EFFECTS OF A SECONDARY SEXUAL CHARACTER AND SONG ON PATERNITY IN THE BARN SWALLOW

Multiple signals may evolve because they provide independent informati on on the condition of a signaler. Females should pay attention to mal e characters relative to their reliability as signals of male attracti veness or quality. Since behavioral traits are flexible and, therefore , subject to strong environmental influences, females should weigh sta ble morphological signals higher in their choice of mates for genetic benefits than flexible behavioral traits, for example, by paying parti cular attention to phenotypically plastic traits when produced in comb ination with an exaggerated morphological signal. Consistent with this prediction, female barn swallows Hirundo rustica, which are known to prefer males with the longest tail feathers (a secondary sexual charac ter), also preferred males with extreme expressions of a behavioral tr ait (song rate), as determined from patterns of paternity assessed by microsatellites. However, a statistical interaction between tail lengt h and song rate implied that song rate was relatively unimportant for males with a short tail but more important for long-tailed males. Sinc e song rate is a flexible behavioral trait, females appear to have res ponded to this flexibility by devaluing the importance of song rate in assessment of unattractive sires.