Mt. Kasigau is the northeastern most of the Eastern Arc Mountains global hotspot and harbours some endemic and threatened species, but little is known about bird community changes along its elevational gradient. We assessed the relationship between bird biodiversity metrics, season, human disturbance, elevation and temperature using mist-netting data collected bi-annually over a 10-year period. Birds were sampled along the mountain's elevational gradient at four elevation levels (858, 1104, 1321 and 1547 m). Bird richness, diversity and evenness decreased with increasing altitude in both dry and wet seasons. Bird abundance declined with increasing elevation for the lower three elevation levels but peaked at the highest elevation. All diversity metrics were higher in the wet season compared to the dry season across all the years. Elevation had a greater effect on species assemblages than season, disturbance and temperature. Temperature had significant effects on abundance, diversity and richness, while disturbance had significant effects on diversity, evenness and richness. We conclude that bird assemblages in Mt. Kasigau are strongly shaped by elevational changes, while temperature and disturbance constitute important factors influencing bird conservation in the face of global warming. Our study highlights that elevation, disturbance and temperature influence bird assemblages along tropical elevational gradients.

中文翻译：

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东非山地森林林下鸟类物种丰富度和群落结构的海拔格局

卡西高山是东弧山全球热点地区的最东北部，栖息着一些特有和受威胁的物种，但人们对鸟类群落沿海拔梯度的变化知之甚少。我们使用十年来每两年收集一次的雾网数据评估了鸟类生物多样性指标、季节、人类干扰、海拔和温度之间的关系。沿着山的海拔梯度在四个海拔高度（858、1104、1321和1547米）对鸟类进行了采样。在旱季和雨季，鸟类的丰富度、多样性和均匀度都随着海拔的升高而降低。对于较低的三个海拔高度，鸟类数量随着海拔的升高而下降，但在最高海拔处达到顶峰。与所有年份的旱季相比，雨季的所有多样性指标都较高。海拔对物种组合的影响比季节、干扰和温度更大。温度对丰度、多样性和丰富度有显着影响，而干扰对多样性、均匀度和丰富度有显着影响。我们得出的结论是，卡西高山的鸟类群落受到海拔变化的强烈影响，而温度和干扰是在全球变暖的情况下影响鸟类保护的重要因素。我们的研究强调，海拔、干扰和温度会影响热带海拔梯度上的鸟类群落。