Effective communication between sexual partners is essential for successful reproduction. Avian parents with biparental incubation need to know how to negotiate, when and who will incubate, and how to harmonize partner exchange at the nest. Although considerable effort has been dedicated to studies of incubation rhythms, few studies have investigated how behavioural signals serve to tighten cooperation between parents. Moreover, existing studies are almost exclusively restricted to species in which long distances between incubating and non-incubating parents prevent continuous communication during incubation. Thus, the most frequently described parental exchange system is a simple model characterized by the return of the non-incubating parent to the nest itself. Here, we propose more complex parental exchange behaviour in the Northern Lapwing (Vanellus vanellus), a territorial species capable of continuous partner communication during incubation and with a highly variable male contribution to incubation. Northern Lapwing females regularly vocalized shortly before departing from the nest, while males mostly left the nest quietly. Responsiveness of the male to female vocalization, perhaps in combination with her flying away from the nest, helped to synchronize incubation care by increasing the probability of exchange, and also by shortening the exchange gaps. In contrast, a male-to-female exchange gap most often occurred after the male quietly flew away from the nest. The frequency of female vocal signalling was not correlated with the male incubation effort on a between-nest scale, but the highest probability of a female-to-male exchange occurred after vocal signalling by females with the most nest-attentive males. Conversely, lowered effort by females to vocalize in the night was accompanied by lower willingness of males to incubate. Our results suggest that (1) that the incubating parent can communicate with the non-incubating partner using sex-specific behavioural signals, and this helps to synchronize parental exchange on the nest, (2) this signalling may combine acoustic and visual cues, and (3) the efficiency of this signalling might influence the overall nest attendance. The presumption that the repertoire of behavioural signals during reproduction will be much more complex in territorial species that are capable of continuous communication between the partners during the incubation period should be further tested.

中文翻译：

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领地鸟类的父母孵化交换涉及性别特异性信号

性伴侣之间的有效沟通对于成功繁殖至关重要。双亲孵化的鸟类父母需要知道如何协商、何时和谁孵化，以及如何协调巢穴中的伙伴交换。尽管已经付出了相当大的努力来研究孵化节奏，但很少有研究调查行为信号如何有助于加强父母之间的合作。此外，现有研究几乎完全限于孵化和非孵化父母之间的长距离阻止孵化期间持续交流的物种。因此，最常被描述的亲代交换系统是一个简单的模型，其特征是非孵化的亲代返回巢穴本身。这里，我们提出了在北田凫（Vanellus vanellus）中更复杂的亲代交换行为，这是一种能够在孵化过程中持续进行伴侣交流的地域性物种，并且雄性对孵化的贡献变化很大。北田凫雌性经常在离开巢穴前不久发出声音，而雄性大多安静地离开巢穴。雄性对雌性发声的反应，也许与她飞离巢穴相结合，有助于通过增加交换的概率和缩短交换间隙来同步孵化护理。相比之下，雄性与雌性之间的交换间隙最常发生在雄性悄悄飞离巢穴之后。雌性声音信号的频率与巢间规模的雄性孵化努力无关，但雌性对雄性交换的最高概率发生在雌性与最关注巢穴的雄性发出声音信号之后。相反，雌性在夜间发声的努力降低伴随着雄性孵化的意愿降低。我们的研究结果表明（1）孵化的父母可以使用性别特异性行为信号与非孵化的伴侣交流，这有助于同步巢中的父母交换，（2）这种信号可以结合听觉和视觉提示，以及(3) 该信号的效率可能会影响整个巢穴出勤率。应该进一步测试在繁殖期间的行为信号库在能够在潜伏期期间伴侣之间持续交流的领土物种中要复杂得多的假设。