Effects of Snow-Related Environmental Variation on Breeding Schedules and Productivity of a High-Altitude Population of Dusky Flycatchers (Empidonax oberholseri)
Effects of Snow-Related Environmental Variation on Breeding Schedules and Productivity of a High-Altitude Population of Dusky Flycatchers (Empidonax oberholseri)
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与雪有关的环境变化对高海拔灰鹟 (Empidonax oberholseri) 繁殖时间表和生产力的影响
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发表时间：
2011
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通讯作者：
M. E. Pereyra
中科院分区：
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作者：
M. E. Pereyra
摘要。在加州内华达山脉中部的提奥加山口，暗捕蝇（Empidonax oberholseri）的繁殖时间表多年来变化很大。最早产蛋日期为5月29日至7月1日，随雪深、融化日期和其他与积雪有关的因素而变化。在研究过程中，在铺设日期上有一个明显的小进步（15年中每年0.52天），这与冬季积雪和春季融化的极端情况有关，这些极端情况与内华达山脉的干湿循环有关。春季积雪通过直接和间接影响温度、融化时间和栖息地可利用性的物候变化来影响繁殖时间。这些变量对产卵日期的影响在第一次产卵的雌性（大多数在6月初）最大，到7月中旬繁殖终止时下降。在大雪年和小雪年之间，蛋的大小和羽翼的产量会发生变化，这是大雪年产卵延迟的直接后果。在积雪较轻的年份，在6月中旬产卵的雌鸟能产下更多的卵，每个巢中羽化的雏鸟更多，如果巢失败，雌鸟更有可能重新筑巢。只有两只雌性在一个季节尝试两次繁殖，而且都是最早繁殖的。对当地环境条件敏感性的季节性下降可能限制了暗捕蝇调整繁殖时间表以适应冬季温度、降水和积雪变化所产生的物候延迟的能力，并可能限制其范围扩大到冬季干旱和春季融化较早的地区。
ABSTRACT. Reproductive schedules of Dusky Flycatchers (Empidonax oberholseri) at Tioga Pass, in the central Sierra Nevada of California, varied considerably among years. Dates of earliest laying ranged from 29 May to 1 July and varied with snow depth, melt dates, and other factors associated with snowpack. A small apparent advance in laying date over the course of the study (0.52 days year-1 over 15 years) was associated with extremes in winter snowpack and spring melt that were related to wet—dry cycles in the Sierra Nevada. Spring snowpack acted on reproductive timing through direct and indirect effects of temperature, melt schedule, and phenological changes in habitat availability. The influence of these variables on laying dates was greatest on the first females to lay (most in early June) and declined through mid-July, when breeding terminated. Clutch size and fledgling production varied between years of heavy and light snowpack as a direct consequence of delayed egg laying in years of heavy snow. In years of light snowpack, females that laid eggs by mid-June produced larger clutches, fledged more young per nest, and were more likely to renest if nest failure occurred. Only two females attempted two broods in a single season, and both were among the first to breed. Seasonal declines in sensitivity to local environmental conditions may constrain the ability of Dusky Flycatchers to adjust breeding schedules to match phenological delays produced by changes in winter temperature, precipitation, and snowpack, and may limit range expansion to areas with arid winters and earlier spring melt.