Wildlife populations can respond to changes in climate conditions by either adapting or moving to areas with preferred climate regimes. We studied nesting responses of two bird species, western bluebird (Sialia mexicana) and ash-throated flycatcher (Myiarchus cinerascens), to changing climate conditions (i.e., rising temperatures and increased drought stress) over 21 years in northern New Mexico. We used data from 1649 nests to assess whether the two species responded to changing climate conditions through phenological shifts in breeding time or shifts in nesting elevation. We also examined changes in reproductive output (i.e., clutch size). Our data show that western bluebirds significantly increased nesting elevation over a 19-year period by approximately 5 m per year. Mean spring temperature was the best predictor of western bluebird nesting elevation. Higher nesting elevations were not correlated with hatch dates or clutch sizes in western bluebirds, suggesting that nesting at higher elevations does not affect breeding time or reproductive output. We did not observe significant changes in nesting elevation or breeding dates in ash-throated flycatchers. Nesting higher in elevation may allow western bluebirds to cope with the increased temperatures and droughts. However, this climate niche conservatism may pose a risk for the conservation of the species if climate change and habitat loss continue to occur. The lack of significant changes detected in nesting elevation, breeding dates, and reproductive output in ash-throated flycatchers suggests a higher tolerance for changing environmental conditions in this species. This is consistent with the population increases reported for flycatchers in areas experiencing dramatic climate changes.

中文翻译：

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响应变化的气候条件，两个北美次生腔n的长期物候

野生动物种群可以通过适应或迁移到气候条件较好的地区来应对气候条件的变化。我们研究了两种鸟类的筑巢响应，即西部蓝鸟（Sialia mexicana）和灰喉fly（Miiarchus cinerascens）），新墨西哥州北部21年以来不断变化的气候条件（例如，温度升高和干旱压力增加）。我们使用来自1649个巢穴的数据来评估这两个物种是通过繁殖时间的物候变化还是筑巢高度的变化来应对气候变化。我们还研究了生殖输出的变化（即离合器的大小）。我们的数据表明，在19年的时间里，西部蓝鸟每年显着增加筑巢高度约5 m。平均春季温度是西方蓝鸟筑巢高度的最佳预测指标。较高的筑巢高度与西部蓝鸟的孵化日期或孵化场的大小无关，这表明在较高的高度筑巢不会影响繁殖时间或繁殖产量。我们没有观察到灰喉fly蝇的筑巢高度或繁殖日期有明显变化。在更高的高度筑巢可能会使西部蓝鸟应对不断增加的温度和干旱。但是，如果气候变化和生境丧失继续发生，这种气候生态位保守性可能会对物种的保护构成风险。在灰喉fly蝇中，没有检测到筑巢高度，繁殖日期和繁殖产量方面的显着变化，这表明该物种对环境条件的适应性更高。据报道，在经历剧烈气候变化的地区，捕蝇器的人口增加与之吻合。但是，如果气候变化和生境丧失继续发生，这种气候生态位保守性可能会对物种的保护构成风险。在灰喉捕蝇器中，没有检测到筑巢高度，繁殖日期和繁殖产量方面的显着变化，这表明该物种对改变环境条件的耐受性更高。据报道，在经历剧烈气候变化的地区，捕蝇器的人口增加与之吻合。但是，如果气候变化和生境丧失继续发生，这种气候生态位保守性可能会对物种的保护构成风险。在灰喉fly蝇中，没有检测到筑巢高度，繁殖日期和繁殖产量方面的显着变化，这表明该物种对环境条件的适应性更高。据报道，在经历剧烈气候变化的地区，捕蝇器的人口增加与之吻合。