VARIABLE MATING PATTERNS IN TASMANIAN NATIVE HENS (GALLINULA-MORTIERII) - CORRELATES OF REPRODUCTIVE SUCCESS

1, The Tasmanian native hen (Gallinula mortierii) exhibits mate-sharin g by both males and females, with monogamy, polyandry, polygyny and po lygynandry all occurring in a single population. 2, Multivariate model s are used to investigate the relationships between reproductive succe ss and a number of aspects of group compositions and territories in a population of Tasmanian native hens studied at Maria Island, Tasmania, Australia, over five breeding seasons. 3. Mating pattern did not rema in a significant explanatory variable in most of the models of the fac tors affecting reproductive success, suggesting that the reproductive success of individuals is not affected by their mating pattern. The on ly exception was that mating pattern was significantly related to clut ch size, because co-breeding females laid combined clutches. 4. Breedi ng success (per group, per breeding male and per breeding female) was most significantly related to the total length of edge between short p asture and tall, dense vegetative cover present in a territory. It is proposed that edges between short pasture and cover allow the Tasmania n native hens' precocious chicks to be near good feeding areas while a lso remaining close to protective cover. 5, Individual components of b reeding success were most significantly related to different variables . The presence of water in the territory increased the probability tha t a group laid eggs. Clutch size was most affected by a group's mating pattern. Hatching success increased with the number of adults in a gr oup. Chick survival increased with the length of pasture/cover edge in a group's territory. 6, The probability that mate-sharing by males oc curred in a group was positively related to the total length of pastur e/cover edge in the group's territory. There was no such relationship for mate-sharing by females. 7, These models suggest that individuals do not incur any net costs from sharing mates and that such sharing ma y allow some individuals to breed in higher-quality territories than t hose to which they would otherwise have access.