ESJ58 一般講演（ポスタ-発表） P3-159
*Fumiaki Y. Nomano （Hokkaido Univ）, Andrew F. Russell （Univ of Exeter, Macquarie Univ）
Studies of parental care typically assume that levels of investment in offspring are determined independently of others. However, this is unlikely to be the case. Cooperative breeding systems are useful for examining social effects on individual contributions to (allo)parental care because the efficient coordination of care among the multiple group members might require observing the behaviour of each other. Chestnut-crowned babblers (Pomatostomus ruficeps) are cooperatively breeding birds endemic to arid, south-eastern Australia, and breed in unusually large groups among birds (2-15). Individuals frequently encounter other individuals when they visit nests, and arrival time is often synchronous (< 1 min). We analysed the patterns of synchronicity in provisioning of this species as social networks. Sequences of arrival at the nest were asymmetric between pairs of individuals. Specifically, yearlings tended to follow adult birds and females tended to follow males. Heterogeneous patterns in synchrony at nest arrival might influence the individual investment and group productivity. The fine description of social networks will facilitate further analyses of cooperative provisioning at dyadic or higher levels.