Abstract In the last decades, western Iberian Mediterranean drylands have experienced a shift from extensive sheep to beef-cattle farming. In this 5-year study in Evora region (Southern Portugal), we investigated the role of livestock species in favouring grassland bird habitat suitability, starting from the hypothesis that livestock species complement bird habitat requirements under contrasting grazing rotation patterns and annual rainfall conditions. Field methods were based on bird counts and data was analysed using Generalized Linear Mixed Models. Model ranking and selection were based on the estimation of second-order Akaike Information Criterion (AICc). The grazing rotation pattern was the variable that best explained bird richness and total bird abundance, whereas livestock species had a minor effect. The corn bunting, the common quail and the crested lark presented higher abundances in fields grazed by sheep whereas calandra larks showed opposite trends. Except for the crested lark, grazing rotation pattern was the variable that best explained the abundance of individual species. Fields under short-medium duration rotational grazing revealed lower bird abundance and richness. Interactions between livestock species and grazing rotation were only found for the zitting cisticola. Bird species preferences relative to livestock species were found to be independent of annual rainfall conditions. We conclude that shifting from sheep to cattle grazing in Iberian Mediterranean drylands may favour light to moderate changes in the species identity of grassland bird assemblages (i.e. certain species appear or increase while others decrease or disappear from the assemblage), although no significant changes were found for bird richness. However, the grazing rotational patterns had greater effect on species total abundance and richness than the particular livestock species. Given the alarming decline of grassland birds in Europe, changes in grassland bird assemblages associated to the sheep-to-cattle shift currently occurring in Iberia may become an important issue within the framework of future European agricultural policy and should be subject to long term monitoring.

中文翻译：

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牲畜种类和放牧轮作模式调节地中海旱地草原鸟类群落

摘要 在过去的几十年里，伊比利亚地中海西部旱地经历了从粗放养羊到肉牛养殖的转变。在埃武拉地区（葡萄牙南部）的这项为期 5 年的研究中，我们调查了牲畜物种在促进草原鸟类栖息地适宜性方面的作用，首先假设牲畜物种在不同的放牧轮作模式和年降雨量条件下补充了鸟类栖息地的要求。现场方法基于鸟类数量，使用广义线性混合模型分析数据。模型排序和选择基于二阶赤池信息准则 (AICc) 的估计。放牧轮作模式是最能解释鸟类丰富度和鸟类总数的变量，而牲畜种类的影响较小。玉米旗布，普通鹌鹑和凤头百灵在绵羊放牧的田地中表现出更高的丰度，而金雀花则表现出相反的趋势。除了凤头百灵，放牧轮作模式是最能解释单个物种丰度的变量。中短时间轮作放牧下的田地显示鸟类的丰度和丰富度较低。仅在 zitting cisticola 中发现了牲畜物种和放牧轮作之间的相互作用。发现相对于牲畜物种的鸟类物种偏好与年降雨量条件无关。我们得出的结论是，在伊比利亚地中海旱地从放羊到放牛的转变可能有利于草原鸟类组合的物种特性的轻度到中度变化（即 某些物种出现或增加，而其他物种从组合中减少或消失），尽管鸟类丰富度没有显着变化。然而，与特定牲畜物种相比，放牧轮作模式对物种总丰度和丰富度的影响更大。鉴于欧洲草原鸟类数量惊人的减少，与伊比利亚目前发生的羊转牛相关的草原鸟类种群变化可能成为未来欧洲农业政策框架内的一个重要问题，应受到长期监测。