The shiny cowbird Molothrus bonariensis parasitizes many species with different life-history traits and has a detrimental effect on the survival of the progeny of the hosts. In response, hosts have developed numerous antiparasitic defenses. Here, we examined the effects of brood parasitism by shiny cowbird on the clutch and brood sizes (83 nests) in a small host, the black-backed water-tyrant Fluvicola albiventer. We also studied whether the death of parasite nestlings was related to the care of the foster parents and whether the host had any antiparasitic defense against the shiny cowbird. Our results indicate that brood parasitism significantly decreased the host hatching and fledging successes. The majority of nest failures (57%) were caused by brood parasitism. Shiny cowbird parasitism occurred in 52% of nests and the intensity of parasitism was 1.23 ± 0.53 eggs per parasitized nest. Of the total host eggs, 54% were damaged. During the incubation stage, 20 nests (47%) were abandoned because of egg punctures by Shiny cowbirds females. Only two parasitic fledglings were recorded, while the remaining nestlings either died from starvation (n = 12) or predation (n = 3). Foster parents abandoned parasitic nestlings between 5 and 10 days old. Our findings demonstrate that the shiny cowbird have very low rates of fledging success when parasitizing black-backed water-tyrant. Also, parasitism had a high reproductive cost in the black-backed water-tyrant because a very low proportion (7%) of the parasitized nests (n = 43) were successful.

中文翻译：

---

闪亮牛鸟 Molothrus bonariensis 的巢寄生对小宿主黑背水霸 Fluvicola albiventer 繁殖成功的影响

闪亮的牛鹂 Molothrus bonariensis 寄生了许多具有不同生活史特征的物种，并对宿主后代的生存产生不利影响。作为回应，宿主已经发展出许多抗寄生虫防御措施。在这里，我们研究了闪亮牛鹂的巢寄生对小型宿主黑背水霸 Fluvicola albiventer 的窝数和巢大小（83 个巢）的影响。我们还研究了寄生虫雏鸟的死亡是否与养父母的照顾有关，以及寄主是否对闪亮牛鹂有任何抗寄生虫防御。我们的结果表明，巢寄生显着降低了宿主的孵化和雏鸟成功率。大多数巢穴失败（57%）是由巢寄生引起的。52%的巢中出现闪亮牛鹂寄生，寄生强度为每个寄生巢1.23±0.53枚卵。寄主卵总数中，54% 受损。在孵化阶段，有 20 个巢穴（47%）因卵被雌性闪亮牛鹂刺破而被遗弃。仅记录了两只寄生雏鸟，其余雏鸟要么死于饥饿（n = 12），要么死于捕食（n = 3）。养父母遗弃了 5 至 10 天大的寄生雏鸟。我们的研究结果表明，当闪亮牛鹂寄生在黑背水霸身上时，其雏鸟成功率非常低。此外，寄生对黑背水霸的繁殖成本很高，因为成功寄生的巢穴（n = 43）的比例非常低（7%）。54% 受损。在孵化阶段，有 20 个巢穴（47%）因卵被雌性闪亮牛鹂刺破而被遗弃。仅记录了两只寄生雏鸟，其余雏鸟要么死于饥饿（n = 12），要么死于捕食（n = 3）。养父母遗弃了 5 至 10 天大的寄生雏鸟。我们的研究结果表明，当闪亮牛鹂寄生在黑背水霸身上时，其雏鸟成功率非常低。此外，寄生对黑背水霸的繁殖成本很高，因为成功寄生的巢穴（n = 43）的比例非常低（7%）。54% 受损。在孵化阶段，有 20 个巢穴（47%）因卵被雌性闪亮牛鹂刺破而被遗弃。仅记录了两只寄生雏鸟，其余雏鸟要么死于饥饿（n = 12），要么死于捕食（n = 3）。养父母遗弃了 5 至 10 天大的寄生雏鸟。我们的研究结果表明，当闪亮牛鹂寄生在黑背水霸身上时，其雏鸟成功率非常低。此外，寄生对黑背水霸的繁殖成本很高，因为成功寄生的巢穴（n = 43）的比例非常低（7%）。而剩下的雏鸟要么死于饥饿（n = 12），要么死于捕食（n = 3）。养父母遗弃了 5 至 10 天大的寄生雏鸟。我们的研究结果表明，当闪亮牛鹂寄生在黑背水霸身上时，其雏鸟成功率非常低。此外，寄生对黑背水霸的繁殖成本很高，因为成功寄生的巢穴（n = 43）的比例非常低（7%）。而剩下的雏鸟要么死于饥饿（n = 12），要么死于捕食（n = 3）。养父母遗弃了 5 至 10 天大的寄生雏鸟。我们的研究结果表明，当闪亮牛鹂寄生在黑背水霸身上时，其雏鸟成功率非常低。此外，寄生对黑背水霸的繁殖成本很高，因为成功寄生的巢穴（n = 43）的比例非常低（7%）。