Predation is the most important factor limiting Northern Hemisphere duck nest survival. While most avian nest predators take only eggs, mammalian predators also pose mortality risks to incubating ducks. Partial depredation of duck clutches elevates subsequent nest desertion probability, especially where eggshells provide evidence of the depredation event. Avian predators tend to consume egg contents at the nest, which may not intrinsically pose a risk to hens, but leave egg remains. This begs the question: does primary avian depredation of duck eggs actively facilitate nest visits by secondary mammalian predators, with potential survival consequences for the remaining clutch, but also sitting hens? We created 335 artificial duck nests in Finland and Denmark during 2017–2019 and monitored them for seven days using wildlife cameras to test whether initial avian predators breaking the eggs facilitated visits by secondary mammalian predators in various duck breeding habitats. Visitation rates of mammalian predators likely to take duck hens increased significantly after avian egg depredation events that involved egg breakage, although rates differed between habitats. Most common mammalian nest visitors at nests depredated by avian predators were red fox (Vulpes vulpes), followed by two alien species, raccoon dog (Nyctereutes procyonoides) and American mink (Neovison vison). Although we should be prudent about extrapolating conclusions from artificial experiment to real duck nests, our results strongly suggest inter-guild facilitation between avian and mammalian predators at duck nest sites. We suggest that by breaking the eggs, avian predators may offer olfactory, visual or other cues for secondary predators. Nest visits by mammalian predators could potentially increase egg depredation risk, but also elevate mortality risks for incubating females, dependent upon prevailing predator guilds.

捕食是限制北半球鸭巢生存的最重要因素。尽管大多数鸟类的巢捕食者只取卵，但哺乳动物的捕食者也给鸭子的孵化带来死亡风险。鸭离合器的部分折旧提高了随后的巢抛弃的可能性，尤其是蛋壳提供了折旧事件的证据时。禽肉食肉动物倾向于在巢中食用鸡蛋，这可能不会从本质上对母鸡构成威胁，但会留下鸡蛋残留。这就引出了一个问题：初级禽鸭捕食活动是否积极地促进了次级哺乳动物捕食者的筑巢造访，从而对其余的食肉鸟造成了潜在的生存后果，还有母鸡？我们在2017-2019年期间在芬兰和丹麦创建了335个人工鸭巢，并使用野生动物照相机对它们进行了为期7天的监测，以测试破坏这些卵的初始禽肉捕食者是否促进了次级哺乳动物捕食者在各种鸭繁殖栖息地的造访。禽蛋掠食事件涉及破蛋后，可能捕食母鸡的哺乳动物捕食者的探视率显着增加，尽管生境之间的比率不同。在被鸟类捕食者淘汰的巢穴中，最常见的哺乳动物巢穴游客是赤狐（禽蛋掠食事件涉及破蛋后，可能捕食母鸡的哺乳动物捕食者的探视率显着增加，尽管生境之间的比率不同。在被鸟类捕食者淘汰的巢穴中，最常见的哺乳动物巢穴游客是赤狐（禽蛋掠食事件涉及破蛋后，可能捕食母鸡的哺乳动物捕食者的探视率显着增加，尽管生境之间的比率不同。在被鸟类捕食者淘汰的巢穴中，最常见的哺乳动物巢穴游客是赤狐（狐狸（Vulpes vulpes），其次是两个外来物种，狗（Nyctereutes procyonoides）和美国水貂（Neovison vison）。尽管我们应该谨慎地将从人工实验得出的结论外推到真正的鸭巢，但我们的结果强烈建议在鸭巢所在地的鸟类和哺乳动物捕食者之间进行行会间的促进。我们建议，通过破坏卵，鸟类的捕食者可能为次级捕食者提供嗅觉，视觉或其他暗示。哺乳动物捕食者的探巢活动可能会增加卵被掠夺的风险，但也会提高孵化雌性的死亡率，这取决于当时流行的捕食者协会。