Am Nat. 2019 Jun;193(6):830-840. doi: 10.1086/703188. Epub 2019 Apr 17.
Joint nesting by females and cooperative polyandry-cooperatively breeding groups with a male-biased breeder sex ratio-are little-understood, rare breeding systems. We tested alternative hypotheses of factors potentially driving these phenomena in a population of joint-nesting acorn woodpeckers (). During periods of high population density and thus low independent breeding opportunities, acorn woodpecker females formed joint-nesting coalitions with close kin. Coalitions were typically associated with groups with a male bias. We found strong evidence for both inter- and intrasexual conflict, as joint nesting conferred a fitness benefit to some males, a significant fitness cost to females, and no gain in per capita reproductive output for either sex. Such conflict, particularly the cost to females, may be an important reason why joint nesting is rare among cooperatively breeding taxa.
雌性共同筑巢和雄性偏多的合作一妻多夫制——合作繁殖群体是了解甚少的、罕见的繁殖系统。我们检验了可能驱动这种现象的各种因素的替代假说，研究对象是一个共同筑巢的橡果啄木鸟（）种群。在种群密度高、独立繁殖机会低的时期，橡果啄木鸟雌性与近亲结成共同筑巢的联盟。这种联盟通常与雄性偏多的群体有关。我们发现了强烈的证据表明存在种内和种间的冲突，因为共同筑巢对一些雄性有利，对雌性有显著的代价，对两性的人均繁殖产出都没有增益。这种冲突，特别是对雌性的代价，可能是共同筑巢在合作繁殖类群中罕见的一个重要原因。
