Within hybrid zones of socially monogamous species, the number of mating opportunities with a conspecific can be limited. As a consequence, individuals may mate with a heterospecific (social) partner despite possible fitness costs to their hybrid offspring. Extra‐pair copulations with a conspecific may thus arise as a possible post hoc strategy to reduce the costs of hybridization. We here assessed the rate of extra‐pair paternity in the hybrid zone between all‐black carrion crows (Corvus (corone) corone) and grey hooded crows (C. (c.) cornix) and tested whether extra‐pair paternity (EPP) was more likely in broods where parents differed in plumage colour. The proportion of broods with at least one extra‐pair offspring and the proportion of extra‐pair offspring were low overall (6.98% and 2.90%, respectively) with no evidence of hybrid broods having higher EPP rates than purebred nests.

中文翻译：

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额外配对作为降低异种繁殖成本的策略？乌鸦杂交区的见解

在社会一夫一妻制物种的杂交区域内，与同种的交配机会数量可能有限。因此，尽管他们的杂交后代可能会付出健康代价，但个体可能会与异种（社会）伴侣交配。因此，与同种异体的额外配对可能会作为一种可能的事后策略来降低杂交成本。我们在这里评估了全黑腐肉乌鸦 (Corvus (corone) corone) 和灰色头巾乌鸦 (C. (c.)cornix) 之间的杂交区中的额外配对率，并测试了额外配对 (EPP)在父母羽毛颜色不同的育雏中更有可能。至少有一对额外后代的比例和额外后代的比例总体较低（6.98％和2.90％，