Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI 53706, U.S.A.
U.S. Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin, Madison, WI 53706, U.S.A.
Conserv Biol. 2018 Aug;32(4):872-882. doi: 10.1111/cobi.13089. Epub 2018 Apr 25.
Grassland birds are declining faster than any other bird guild across North America. Shrinking ranges and population declines are attributed to widespread habitat loss and increasingly fragmented landscapes of agriculture and other land uses that are misaligned with grassland bird conservation. Concurrent with habitat loss and degradation, temperate grasslands have been disproportionally affected by climate change relative to most other terrestrial biomes. Distributions of grassland birds often correlate with gradients in climate, but few researchers have explored the consequences of weather on the demography of grassland birds inhabiting a range of grassland fragments. To do so, we modeled the effects of temperature and precipitation on nesting success rates of 12 grassland bird species inhabiting a range of grassland patches across North America (21,000 nests from 81 individual studies). Higher amounts of precipitation in the preceding year were associated with higher nesting success, but wetter conditions during the active breeding season reduced nesting success. Extremely cold or hot conditions during the early breeding season were associated with lower rates of nesting success. The direct and indirect influence of temperature and precipitation on nesting success was moderated by grassland patch size. The positive effects of precipitation in the preceding year on nesting success were strongest in relatively small grassland patches and had little effect in large patches. Conversely, warm temperatures reduced nesting success in small grassland patches but increased nesting success in large patches. Mechanisms underlying these differences may be patch-size-induced variation in microclimates and predator activity. Although the exact cause is unclear, large grassland patches, the most common metric of grassland conservation, appears to moderate the effects of weather on grassland-bird demography and could be an effective component of climate-change adaptation.
草原鸟类在北美的所有鸟类中下降速度最快。其分布范围缩小和数量减少归因于广泛的栖息地丧失以及农业和其他土地利用的景观日益碎片化，而这些土地利用方式与草原鸟类保护不匹配。与栖息地丧失和退化相伴而生的是，相对于大多数其他陆地生物群系，温带草原受到气候变化的不成比例影响。草原鸟类的分布通常与气候梯度相关，但很少有研究人员探索过天气对栖息在一系列草原片段中的草原鸟类种群动态的影响。为此，我们模拟了温度和降水对栖息在北美的一系列草原斑块中的 12 种草原鸟类筑巢成功率的影响（来自 81 项单独研究的 21000 个鸟巢）。前一年降水较多与筑巢成功率较高相关，但繁殖季节降水较多会降低筑巢成功率。繁殖季节早期的极端寒冷或炎热条件与较低的筑巢成功率相关。温度和降水对筑巢成功率的直接和间接影响受到草原斑块大小的调节。前一年降水对筑巢成功率的积极影响在相对较小的草原斑块中最强，而在大斑块中几乎没有影响。相反，温暖的温度降低了小草原斑块中的筑巢成功率，但增加了大斑块中的筑巢成功率。这些差异的潜在机制可能是斑块大小引起的小气候和捕食者活动的变化。尽管确切原因尚不清楚，但作为草原保护最常见的指标的大面积草原斑块似乎调节了天气对草原鸟类种群动态的影响，并且可能是适应气候变化的有效组成部分。
