Department of Biological Sciences and Raptor Research Center, Boise State University, Boise, ID, USA.
Department of Biology, Montclair State University, Montclair, NJ, USA.
Oecologia. 2022 May;199(1):91-102. doi: 10.1007/s00442-022-05169-w. Epub 2022 Apr 22.
Birds aim to optimize resources for feeding young and self-maintenance by timing reproduction to coincide with peak food availability. When reproduction is mistimed, birds could incur costs that affect their survival. We studied whether nesting phenology correlated with the apparent survival of American kestrels (Falco sparverius) from two distinct populations and examined trends in clutch-initiation dates. We estimated apparent survival using multi-state mark-recapture models with nesting timing, nesting success, sex, age, and weather covariates. Nesting timing predicted the apparent survival of successful adults; however, the effect differed between populations. Early nesting kestrels had higher apparent survival than later nesters in the western population, where kestrels have a relatively long nesting season. At the eastern site, where kestrels have a relatively short nesting season, the pattern was reversed-later nesters had higher apparent survival than earlier nesters. Nesting timing did not affect the apparent survival of adults with failed nests suggesting that the energetic cost of producing fledglings contributed to the timing effect. Finally, clutch-initiation dates advanced in the western population and remained static in the eastern population. Given that both populations have seasonal declines in productivity, population-specific survival patterns provide insight into seasonal trade-offs. Specifically, nesting timing effects on survival paralleled productivity declines in the western population and inverse patterns of survival and reproduction in the eastern population suggest a condition-dependent trade-off. Concomitant seasonal declines in reproduction and survival may facilitate population-level responses to earlier springs, whereas seasonal trade-offs may constrain phenology shifts and increase vulnerability to mismatch.
鸟类通过将繁殖时间与食物供应高峰期相吻合，旨在优化喂养幼鸟和自我维持的资源。当繁殖时机不合适时，鸟类可能会承担影响其生存的成本。我们研究了两个不同种群的美洲红隼（Falco sparverius）的筑巢物候是否与明显的存活率相关，并检查了产卵日期的趋势。我们使用带有筑巢时间、筑巢成功率、性别、年龄和天气协变量的多状态标记重捕模型来估计明显的存活率。筑巢时间预测了成功成年个体的明显存活率；然而，这种影响在两个种群之间有所不同。在西部种群中，早期筑巢的红隼比晚期筑巢的红隼具有更高的明显存活率，而在西部种群中，红隼的筑巢季节相对较长。在东部地区，红隼的筑巢季节相对较短，情况正好相反，即晚期筑巢的红隼比早期筑巢的红隼具有更高的明显存活率。筑巢时间不会影响未筑巢的成年个体的明显存活率，这表明产雏的能量成本导致了这种时间效应。最后，西部种群的产卵起始日期提前，而东部种群的产卵起始日期保持不变。鉴于两个种群的生产力都有季节性下降，特定种群的生存模式提供了对季节性权衡的深入了解。具体而言，筑巢时间对生存的影响与西部种群生产力下降相吻合，而东部种群生存和繁殖的反向模式表明存在条件依赖的权衡。繁殖和生存的同期季节性下降可能有助于种群对更早春天的反应，而季节性权衡可能限制物候变化并增加不匹配的脆弱性。
