Jarrett Crinan, Simon Ojodomo Godday, Tchana Christian N, Pev Thaddeus Apezan, Meigang Kamkeng Michelle Fany, Wandji Alain Christel, Manu Shiiwua A, Tchoumbou Mélanie Adèle, Helm Barbara, Powell Luke L, Nwaogu Chima J
Swiss Ornithological Institute Bird Migration Unit Sempach Switzerland.
School of Biodiversity, One Health and Veterinary Medicine, College of Medical, Veterinary and Life Sciences University of Glasgow Glasgow UK.
Ecol Evol. 2024 Sep 11;14(9):e70274. doi: 10.1002/ece3.70274. eCollection 2024 Sep.
Birds time their life cycle events to favourable windows in environmental conditions. In tropical environments, where photoperiod variation is small, birds show high variability in the timing of life cycle stages, yet these species have been severely underrepresented in phenology research. Here, we investigated temporal patterns in bird life cycles and resource availability in two sites in tropical Africa: Weppa (Nigeria, 7° N) and Elat (Cameroon, 3° N). In these sites we captured common bulbuls (), a widespread generalist, and recorded breeding and moult over a 12-month period. Simultaneously, we surveyed fruiting tree and arthropod abundance. Our aim was to quantify seasonal patterns in moult and breeding in bulbuls at both sites, and link them to fluctuations in local fruit and arthropod abundance and precipitation. Moult was more seasonal than breeding in both sites, and seasonality of both life cycle events was stronger in Nigeria than Cameroon. The peak timing for moult was 1.5 months earlier in Nigeria than Cameroon. Seasonal variation in abundance of fruiting trees and arthropods was different between sites, as were the associations with breeding and moulting. In Nigeria, we found a positive association between moult and arthropod abundance, and a negative one with fruiting tree abundance. In contrast, in Cameroon moult was associated with higher precipitation, while breeding occurred at times with higher fruit abundance. Our results provide evidence that, even in similar habitats separated by four degrees in latitude, seasonal patterns across three trophic levels are variable. Understanding links between environmental conditions and life cycle events can reveal potential vulnerabilities of tropical species, and guide conservation efforts.
鸟类会根据环境条件中的有利时机来安排其生命周期事件。在热带环境中，光周期变化较小，鸟类在生命周期各阶段的时间安排上表现出高度的变异性，但这些物种在物候研究中的代表性一直严重不足。在这里，我们调查了热带非洲两个地点鸟类生命周期和资源可利用性的时间模式：韦帕（尼日利亚，北纬7°）和埃拉特（喀麦隆，北纬3°）。在这些地点，我们捕获了普通鹎（一种分布广泛的杂食性鸟类），并记录了它们在12个月内的繁殖和换羽情况。同时，我们调查了结果树和节肢动物的数量。我们的目的是量化这两个地点鹎的换羽和繁殖的季节性模式，并将它们与当地水果和节肢动物数量以及降水的波动联系起来。在这两个地点，换羽比繁殖更具季节性，并且这两个生命周期事件的季节性在尼日利亚比在喀麦隆更强。尼日利亚换羽的高峰期比喀麦隆早1.5个月。不同地点结果树和节肢动物数量的季节性变化不同，它们与繁殖和换羽的关联也不同。在尼日利亚，我们发现换羽与节肢动物数量呈正相关，与结果树数量呈负相关。相比之下，在喀麦隆，换羽与较高的降水量有关，而繁殖发生在水果数量较多的时候。我们的结果表明，即使在纬度相差4度的相似栖息地中，三个营养级的季节性模式也是可变的。了解环境条件与生命周期事件之间的联系可以揭示热带物种潜在的脆弱性，并指导保护工作。
