Patterns of mate-sharing in a population of Tasmanian Native Hens Gallinula mortierii

We present data on patterns of mate-sharing collected during a seven-year study of Tasmanian Native Hens Gallinula mortierii at Maria Island, off the east coast of Tasmania, Australia. At this site, Tasmanian Native Hens lived in groups of two to 13 birds that defended all-purpose territories. Monogamy, polyandry, polygyny and polygynandry all occurred in this population each year, with polygynous and polygynandrous females laying joint clutches. When mate-sharing occurred, whether by males or females, co-breeders were usually related. Data on the numbers of copulations, mounts and attempted mounts exhibited by co-breeders of the same sex showed that there was a high level of variation in the degree of sharing of copulations among co-breeders in this population, with males generally sharing copulations more evenly than females. In addition, many groups contained reproductively mature one- or two-year old individuals that were not involved in sexual behaviour.