Most birds rely on cooperation between pair partners for breeding. In long-term monogamous species, pair bonds are considered the basic units of social organization, albeit these birds often form foraging, roosting or breeding groups in which they repeatedly interact with numerous conspecifics. Focusing on jackdaws Corvus monedula, we here investigated 1) the interplay between pair bond and group dynamics in several social contexts and 2) how pair partners differ in individual effort of pair bond maintenance. Based on long-term data on free-flying birds, we quantified social interactions between group members within three positive contexts (spatial proximity, feeding and sociopositive interactions) for different periods of the year (non-breeding, pre-breeding, parental care). On the group level, we found that the number of interaction partners was highest in the spatial proximity context while in the feeding and sociopositive contexts the number of interaction partners was low and moderately low, respectively. Interactions were reciprocated within almost all contexts and periods. Investigating subgrouping within the flock, results showed that interactions were preferentially directed towards the respective pair partner compared to unmated adults. When determining pair partner effort, both sexes similarly invested most into mutual proximity during late winter, thereby refreshing their bond before the onset of breeding. Paired males fed their mates over the entire year at similar rates while paired females hardly fed their mates at all but engaged in sociopositive behaviors instead. We conclude that jackdaws actively seek out positive social ties to flock members (close proximity, sociopositive behavior), at certain times of the year. Thus, the group functions as a dynamic social unit, nested within are highly cooperative pair bonds. Both sexes invested into the bond with different social behaviors and different levels of effort, yet these are likely male and female proximate mechanisms aimed at maintaining and perpetuating the pair bond.

中文翻译：

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自由飞行的寒鸦Corvus monedula的配对键特征和维持：社会背景和季节的影响


大多数鸟类依靠配对伙伴之间的合作进行繁殖。在长期实行一夫一妻制的物种中，配对关系被认为是社会组织的基本单位，尽管这些鸟类经常形成觅食、栖息或繁殖群体，在群体中它们与众多同种动物反复互动。我们以寒鸦 Corvus monedula 为重点，研究了 1) 几种社会背景下配对关系与群体动态之间的相互作用，以及 2) 配对伙伴在维持配对关系方面的个人努力有何不同。根据自由飞翔鸟类的长期数据，我们量化了一年中不同时期（非繁殖、繁殖前、父母照顾）三种积极环境（空间接近、进食和社会积极互动）下群体成员之间的社会互动。在群体层面上，我们发现，在空间邻近环境中互动伙伴的数量最多，而在喂养和社会积极环境中，互动伙伴的数量分别较低和中等偏低。几乎在所有背景和时期内，互动都是相互的。对鸡群内的亚群进行调查，结果表明，与未交配的成虫相比，相互作用优先针对各自的配对伙伴。在确定配对伴侣的努力时，两性在冬末同样将大部分精力投入到相互接近上，从而在繁殖开始前刷新他们的联系。配对的雄性全年以相似的速度喂养它们的伴侣，而配对的雌性则几乎不喂养它们的伴侣，而是从事社会积极行为。我们得出的结论是，寒鸦在一年中的某些时间积极寻求与群体成员的积极社会关系（近距离、社会积极行为）。 因此，群体作为一个动态的社会单位发挥作用，嵌套在高度合作的配对纽带中。两性都以不同的社会行为和不同程度的努力投入到这种关系中，但这些可能是男性和女性的近似机制，旨在维持和延续夫妻关系。