National Research Council, Institute of Marine Sciences (CNR-ISMAR), Venezia, Italy.
Museum Heineanum, Halberstadt, Germany.
J Anim Ecol. 2021 May;90(5):1071-1084. doi: 10.1111/1365-2656.13432. Epub 2021 Feb 21.
Relevance of breeding season fecundity as a driver of population dynamics has been highlighted by many studies. Despite that, knowledge about how brood type specific (i.e. first, second or replacement) fecundity affects demography of multiple-brooded species is limited. In fact, estimation of brood type specific fecundity is often challenging due to imperfect detection of nesting attempts. We examined the demographic contribution and the feedback on population density of different components of fecundity, along with other vital rates, in a facultative multiple-brooded migratory bird. We used a novel formulation of a fecundity model that allows incorporating reproductive data for which information on the type of brood was unknown in some cases, and embedded it into an integrated population model (IPM) to obtain consensual estimates of all demographic rates, including brood type specific fecundities, reproductive success probabilities and proportion of breeding pairs that performed a second or replacement brood. We then conducted transient life table response experiments on IPM estimates to account for non-stationary environments. We applied the model to two 20-year datasets collected in a Swiss and a German local population of wrynecks Jynx torquilla. Brood type specific fecundities and temporal patterns of brood type specific probabilities of success, number of successful and unsuccessful first broods, probability of starting a second or a replacement brood and proportion of pairs that performed a second or a replacement brood differed between the two populations. However, changes in immigration rate and apparent survival were the dominant contributors to temporal variation and large sequential changes in realized population growth rates in both populations. In the Swiss population we also found that second brood fecundity declined when population size increased. Our study provides insight into the reproductive processes that affect population dynamics and mediate density-dependent fecundity in a migratory bird. In addition, the analytical approach proposed can be used in other studies of multiple-brooded species to maximize the use of available fecundity data through the estimation of unknown brood types, thus favouring a better understanding of the demographic contribution of brood type specific fecundity.
繁殖季节的生殖力与种群动态的关系已被许多研究强调。尽管如此，关于特定窝卵数（即第一窝、第二窝或替代窝）的生殖力如何影响多窝物种的种群动态的知识仍然有限。事实上，由于对巢筑尝试的不完全检测，估计特定窝卵数的生殖力往往具有挑战性。我们研究了在一个兼性多窝候鸟中，不同生殖力成分（包括未知窝卵类型的生殖力）以及其他生命参数对种群密度的贡献和反馈。我们使用了一种新颖的生殖力模型公式，该公式允许纳入在某些情况下未知窝卵类型的繁殖数据，并将其嵌入综合种群模型（IPM）中，以获得所有人口统计率的一致估计，包括特定窝卵数的生殖力、繁殖成功率概率和进行第二窝或替代窝的繁殖对的比例。然后，我们对 IPM 估计值进行了瞬态生命表响应实验，以考虑非稳定环境。我们将模型应用于两个在瑞士和德国的林鸲种群中收集的 20 年数据集。两个种群的特定窝卵数的生殖力和特定窝卵数的成功概率的时间模式、第一窝成功和不成功的窝卵数、开始第二窝或替代窝的概率以及进行第二窝或替代窝的对的比例均不同。然而，移民率和明显存活率的变化是两个种群中时间变化和实现的种群增长率的大序列变化的主要贡献者。在瑞士种群中，我们还发现当种群规模增加时，第二窝的生殖力下降。我们的研究提供了对影响种群动态并调节候鸟中密度依赖生殖力的生殖过程的深入了解。此外，所提出的分析方法可用于其他多窝物种的研究中，通过估计未知的窝卵类型，最大限度地利用可用的生殖力数据，从而更好地理解特定窝卵数的生殖力对种群动态的贡献。
