Climate change, including directional shifts in weather averages and extremes and increased interannual weather variation, is influencing demography and distributions for many bird species. The Ouachita Mountains ecoregion in southeast Oklahoma and west-central Arkansas contains 2 populations of the Red-cockaded Woodpecker (Dryobates borealis, RCW), a federally endangered, cooperatively breeding species. Since this region is at the RCW’s northwestern range periphery, ecological thresholds likely are limiting for the species. Therefore, populations in this region may be more sensitive to climate change-associated weather variation and unpredictability. We used 26 years of nesting data (1991–2016) from the 2 RCW populations to determine if interannual weather variation has affected nesting phenology and productivity. For each population, we used daily temperature and precipitation data for 3 periods (30 and 60 days before nesting; 40 days overlapping the nesting period) to determine how weather influences median nesting date and average clutch size and numbers of fledglings. In a separate analysis, we used shorter time windows with individual nests as replicates to determine how discrete weather events (e.g., minimum and maximum temperatures and intense precipitation events) affect nest success and partial brood loss. For both Oklahoma and Arkansas populations, warmer early spring temperatures generally advanced nesting and increased clutch size and fledgling number. However, the effects of average precipitation varied depending on the amount and duration of precipitation in different time periods. At the nest level, most variables reflecting discrete temperature and precipitation events were unrelated to nest success and brood loss, suggesting that factors other than weather (e.g., habitat quality and predation) more strongly influenced the nesting output of individual RCW broods. Our results indicate RCWs are responding to interannual weather variation in complex and variable ways. However, warming trends may generally be having positive effects on the species at the northwestern edge of its range.

中文翻译：

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年际气候变化影响红冠啄木鸟在其范围西北边缘的筑巢日期和筑巢生产力

气候变化，包括天气平均值和极端天气的方向变化以及年际天气变化的增加，正在影响许多鸟类的人口统计和分布。俄克拉荷马州东南部和阿肯色州中西部的 Ouachita 山脉生态区包含 2 个红冠啄木鸟（Dryobates borealis，RCW）种群，这是一种联邦濒临灭绝的合作繁殖物种。由于该地区位于 RCW 的西北范围外围，因此生态阈值可能会限制该物种。因此，该地区的人口可能对气候变化相关的天气变化和不可预测性更敏感。我们使用来自 2 个 RCW 种群的 26 年筑巢数据（1991-2016）来确定年际天气变化是否影响筑巢物候和生产力。对于每个人口，我们使用 3 个时期（筑巢前 30 天和 60 天；与筑巢期重叠 40 天）的每日温度和降水数据来确定天气如何影响中值筑巢日期和平均离合器大小和雏鸟数量。在单独的分析中，我们使用较短的时间窗口，将单个巢穴作为复制品，以确定离散的天气事件（例如，最低和最高温度以及强烈的降水事件）如何影响巢穴成功和部分育雏损失。对于俄克拉荷马州和阿肯色州的种群而言，早春气温升高通常会促进筑巢并增加离合器大小和雏鸟数量。然而，平均降水量的影响因不同时期降水量和降水持续时间而异。在巢穴层面，大多数反映离散温度和降水事件的变量与筑巢成功和育雏损失无关，这表明天气以外的因素（例如，栖息地质量和捕食）对单个 RCW 育雏的筑巢产量影响更大。我们的结果表明，RCW 正在以复杂多变的方式应对年际天气变化。然而，变暖趋势通常可能对其分布范围西北边缘的物种产生积极影响。