Embryonic vocalisations mediate parental care in Masked Lapwings (Vanellus miles) but not Red-capped Plovers (Charadrius ruficapillus)

Embryonic vocalisations in birds may enable communication between embryos and incubating parents but responses of parents to embryonic vocalisations have not been measured experimentally. In two ground-nesting shorebirds, we compare parental care of eggs without embryonic vocalisations, those with natural embryonic vocalisations, and those in which we experimentally introduced embryonic vocalisations, while accounting for prevailing temperatures. We continuously recorded nests (one block of up to 24 hours per nest) of two ground-nesting shorebirds, the Red-capped Plover Charadrius ruficapillus and Masked Lapwing Vanellus miles and quantified parental behaviours. We predict an increase in egg thermoregulation behaviours (time spent incubating or shading) and ‘fussing’ (a combination of rising and re-settling, shuffling, orientation change and egg turning), when vocalisations were naturally present or when they were experimentally introduced in comparison to when no vocalisations were present (control). In lapwings, the rate of fussing increased at the nest only when natural vocalisations were present, however, preening increased when natural or introduced vocalisations were present. Additionally, the frequency of bill to egg touches (inspections) increased only in the presence of introduced vocalisations. For plovers, treatment had no influence on parental behavioural, however, the frequency of fussing, bill to egg touches, and shell tossing increased with air temperature. For both species, there was no influence of the presence of embryo’s vocalisations (natural or introduced) on the parent’s egg thermoregulation behaviours. Our results highlight that acoustic communication across the eggshell may occur and can influence parental care in shorebirds but appears to be species-specific.鸟类的胚胎发声或许可实现胚胎与孵育亲代间的通讯，但目前尚无实验测量亲代对胚胎发声的应答反应。本研究针对两种地面筑巢的滨鸟，设置三组处理：无胚胎发声的卵、带有自然胚胎发声的卵，以及经实验引入胚胎发声的卵，并控制环境温度变量，比较三组的亲代抚育行为。我们对两种地面筑巢滨鸟——红顶鸻（*Charadrius ruficapillus*）和斑麦鸡（*Vanellus miles*）的巢进行连续录制（每巢单次录制时长不超过24小时），并量化其亲代行为。我们提出如下假设：相较于无胚胎发声的对照组，当存在自然胚胎发声或经实验引入胚胎发声时，亲代的卵温调节行为（孵卵或遮阴时长）以及‘翻整行为’（起身-落定、踱步、调整朝向与翻卵的组合动作）频次将有所提升。对于斑麦鸡而言，仅当存在自然胚胎发声时，巢内翻整行为的发生率才会上升；而当存在自然或实验引入的胚胎发声时，其理羽行为频次则会增加。此外，仅当存在实验引入的胚胎发声时，喙触卵（亲代卵部检查动作）的发生频率才会提升。对于红顶鸻而言，实验处理对其亲代行为无显著影响，但翻整行为、喙触卵频次以及卵壳抛扔行为的发生频率会随环境气温升高而增加。对于两种鸟类而言，胚胎发声（自然或实验引入）的存在与否均未对亲代的卵温调节行为产生显著影响。本研究结果表明，卵壳介导的声学通讯或真实存在，且可对滨鸟的亲代抚育行为产生影响，但这种影响似乎具有物种特异性。