社會性動物除了彼此合作獲取共同利益外，亦需與群體成員競爭共有的資源，因此有許多研究致力於了解動物如何解決這樣的群體衝突，以維持穩定的合作。然而，近年對於非親緣間合作的研究，多把其合作的形成視為利己行為(self-serving behavior)的副產品，忽略合作者彼此行為的影響，亦缺乏防止投機者(free-riders)過度消耗共有利益、破壞合作關係的探討。集體行動問題(collective action problem)適當地闡述當群體利益為低排他、低消耗性時，投機者可經由較少的貢獻取得群體利益的困境；而競合策略(co-opetition)恰可利用其競爭策略與創造群體利益為同一行為的特性，解決這樣的困境。冠羽畫眉(Yuhina brunneiceps)具有多對非親緣者共用一巢的合作生殖系統，正適合以其孵蛋期間的親代照護情形驗證這樣的策略。本研究利用注射感應晶片、架設感應線圈和攝影設備於冠羽畫眉巢邊，於2004-2007年收集繁殖季期間各繁殖群成鳥孵蛋、餵食、與幼鳥取食的資料。結果發現，夜孵起始者多為第一天下蛋者，且負擔大部分的夜孵工作及較大比例的白天孵蛋工作，並在非同歩孵化的巢中擁有體重較重的子代。此結果似乎與非對稱性利益能減低成員投資程度衝突的論述相符，但不同於過去研究中的非對稱性利益為一定值，個體視子代的數量或親緣性而決定其投資；本研究發現藉由競合策略個體不僅可改變其利益，同時因應此利益調整其投資，更因利益取得與付出調整的同時性，而對投機者有較佳的抑制能力，進而維持群體的穩定合作。

Conflict resolution is important for social animals which cooperate and compete with their group members simultaneously. Nevertheless, cooperation among non-kin is regarded as by-product of self-serving behaviors in recent researches, failing to consider the influence of partner''s behaviors and the problem of free-riding. Collective action problems describe the scenario that if group benefits are non-excludable, free-riders can gain the benefits with fewer contribution. Moreover, co-opetition, the strategy to cooperate and compete at the same time, can resolve such dilemma through the changeable payoff and the timing it works. Taiwan yuhina (Yuhina brunneiceps) has a joint-nesting breeding system in which several genetic unrelated pairs breed in a single nest. In this scenario, the incubation period, only one individual working at a time but benefiting the whole clutch, is especially suited for testing the co-opetition strategy. We collected data of parental investments and nestlings food obtaining abilities by injecting transponders and setting up antennas and cameras at the nests. In this study, we found that although individuals who started the nocturnal incubation were usually the first-day layers and invested more both in diurnal and nocturnal incubation, they had heavier nestlings in asynchronous-hatching clutches in return. The result seemingly matches the hypothesis that asymmetric benefits can reduce the conflicts over investments of group members. However, different from investing according to the pre-determined payoff in asymmetric benefit, our study demonstrated that the superiority can also be the offspring quality, which can be obtained by the strategy of parental care. Therefore, co-opetition strategy has the advantage in the timing it works, changing payoff and adjusting investment simultaneously, so has the better capability in inhibiting free-riders and maintains the stable cooperation among groups.

誌謝…………………………………………………………………………………………I
中文摘要…………………………………………………………………………………II
Abstract……………………………………………………………………………III
Contents……………………………………………………………………………IV
Contents of table……………………………………………………V
Contents of figures………………………………………………VI
Introduction…………………………………………………………………1
Material and methods……………………………………………5
Study species………………………………………………………………5
Field methods………………………………………………………………5
Data sampling………………………………………………………………6
Statistical analysis……………………………………………7
Results………………………………………………………………………………9
Discussion………………………………………………………………………11
Reference…………………………………………………………………………14
Table……………………………………………………………………………………18
Figure…………………………………………………………………………………19

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