Male-Male Competition and Mating Success on Leks Attended by Hybrid Prairie-Chicken

Male-male competition contributes to male mating success in lekking birds, however, female choice is usually considered to be responsible for the characteristic skew in fitness among males in this mating system. I conducted intensive behavioral observations during the 2002 breeding season at two leks attended by lesser (Tympanuchus pallidicinctus), greater (T. cupido), and resultant hybrid prairie-chicken in western Kansas, following a regional-scale survey for mixed Tympanuchus leks in 2001. Sample observations of 43 individually marked males over 512 hours allowed identification of agonistic correlates of mating success, which included agonistic display behaviors, court characteristics, and attendance. I then examined how these traits differed among hybrids and their parental forms, and speculated on how hybrid status might affect mating success. Male-male competition appeared to contribute significantly to mating success in lesser and greater prairie-chicken; a total of 24 copulations were observed on the two study leks. A total of five lesser x greater prairie-chicken hybrids regularly attended and displayed; this study is the first to provide behavioral data from marked hybrids on leks. Hybrid males appeared to succeed in the male-male facet of sexual selection as indicated by regular lek attendance, central court placement, court placement adjacent to copulation hotspots, and frequencies of agonistic interactions and vocalizations that were similar to males that mated; yet hybrids failed to copulate. Vocalizations were the primary difference I detected among lesser, greater and hybrid prairie-chicken. I hypothesized that one of these vocalizations, the antiphonal boom, might be subject to intense intrasexual selection. I also provide evidence for the possible role of this vocalization in the recent evolutionary divergence of Tympanuchus.