Cuckoo host use

The breeding success of brood parasites relies on the host’s ability to raise their offspring. Brood parasites might cue on host phenotypes to parasitize high-quality individuals to maximize the likelihood of their offspring fledging. However, parasite preference for high-quality hosts will be dependent on the availability of having multiple nests as options to parasitize. Using long-term data from the common redstart (Phoenicurus phoenicurus), a regular host of the common cuckoo (Cuculus canorus), I tested if cuckoos selectively parasitize redstarts based on phenotypic proxies of individual quality. Morphometrics of breeding redstart adults, redstart and cuckoo nestlings were measured, and body condition was calculated for all. I first evaluated the extent of availability of redstart nests to cuckoos during each parasitism event. Host nest availability is a requirement when testing brood parasite host preference because brood parasites can only be selective when multiple host nests are available within their territories. I found that for at least 75% of nest parasitism events (59 of 78 nest), cuckoo females had other nests available to be parasitized within 1 km. Second, I tested the link between nestling size and the phenotypic traits of the parents and found that larger redstart adults raised larger redstart chicks, and females with higher body condition raised redstart chicks with higher body condition. Lastly, I tested the likelihood of redstart individuals being parasitized as a function of their traits, and the consequences for cuckoo nestlings in terms of their size and condition. I found that once the host nest availability was considered, redstart females with higher body condition had a higher likelihood of being parasitised. However, I found no evidence that cuckoo nestlings benefit from being reared by redstart females with higher body condition. As brood parasites have limited options for impacting their offspring’s development, non-random host use based on host quality seems may be particularly important for parasite’s fitness.

巢寄生生物的繁殖成功率依赖于宿主抚养后代的能力。巢寄生生物可能会根据宿主的表型特征来识别优质个体，以寄生之，从而最大化其后代成功离巢的可能性。然而，对于优质宿主的偏好将取决于可供寄生的多个巢穴的可用性。通过利用来自普通红腹鸟（Phoenicurus phoenicurus）的长期数据，该鸟是普通杜鹃（Cuculus canorus）的常规宿主，本研究旨在检验杜鹃是否基于个体品质的表型代理选择性地寄生红腹鸟。对繁殖期红腹鸟成鸟、红腹鸟与杜鹃雏鸟的形态计量学进行了测量，并对所有个体计算了体况。首先，我评估了红腹鸟巢穴在每次寄生事件中对杜鹃的可用程度。在测试巢寄生生物的宿主偏好时，宿主巢穴的可用性是一个必要条件，因为巢寄生生物只能在它们领地内存在多个宿主巢穴时才能表现出选择性。我发现，在至少75%的巢穴寄生事件（78个巢穴中的59个）中，杜鹃雌鸟在1公里范围内有其他巢穴可供寄生。其次，我测试了巢穴雏鸟大小与父母亲的表型特征之间的联系，发现体型较大的红腹鸟成鸟抚养的雏鸟体型也较大，体况较好的雌鸟抚养的雏鸟体况也较好。最后，我测试了红腹鸟个体被寄生的可能性作为其特征的功能，以及这对于杜鹃雏鸟在体型和体况方面的后果。我发现，在考虑宿主巢穴的可用性后，体况较好的红腹鸟雌鸟被寄生的可能性更高。然而，我没有发现杜鹃雏鸟从被体况较好的红腹鸟雌鸟抚养中获益的证据。由于巢寄生生物对其后代发展的影响有限，基于宿主品质的非随机宿主利用可能对寄生虫的适应性尤为重要。