Waite Thomas A, Strickland Dan
Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH 43210-1293, USA.
Proc Biol Sci. 2006 Nov 22;273(1603):2809-13. doi: 10.1098/rspb.2006.3667.
Population declines along the lower-latitude edge of a species' range may be diagnostic of climate change. We report evidence that climate change has contributed to deteriorating reproductive success in a rapidly declining population of the grey jay (Perisoreus canadensis) at the southern edge of its range. This non-migratory bird of boreal and subalpine forest lives on permanent territories, where it hoards enormous amounts of food for winter and then breeds very early, under still-wintry conditions. We hypothesized that warmer autumns have increased the perishability of hoards and compromised subsequent breeding attempts. Our analysis confirmed that warm autumns, especially when followed by cold late winters, have led to delayed breeding and reduced reproductive success. Our findings uniquely show that weather months before the breeding season impact the timing and success of breeding. Warm autumns apparently represent hostile conditions for this species, because it relies on cold storage. Our study population may be especially vulnerable, because it is situated at the southern edge of the range, where the potential for hoard rot is most pronounced. This population's demise may signal a climate-driven range contraction through local extinctions along the trailing edge.
物种分布范围低纬度边缘的种群数量下降可能是气候变化的诊断依据。我们报告了证据表明，气候变化导致了灰噪鸦（Perisoreus canadensis）在其分布范围南部边缘迅速减少的种群中繁殖成功率下降。这种栖息于北方和亚高山森林的非候鸟生活在固定领地，在那里它会储存大量食物以备冬季之需，然后在仍处于冬季的条件下很早就开始繁殖。我们推测温暖的秋季增加了储存食物的易腐性，并影响了随后的繁殖尝试。我们的分析证实，温暖的秋季，尤其是随后紧接着寒冷的晚冬，会导致繁殖延迟和繁殖成功率降低。我们的研究结果独特地表明，繁殖季节前几个月的天气会影响繁殖的时间和成功率。温暖的秋季显然对该物种来说是不利条件，因为它依赖于冷藏储存。我们研究的种群可能特别脆弱，因为它位于分布范围的南部边缘，在那里储存食物腐烂的可能性最为明显。这一种群的灭绝可能预示着通过后缘局部灭绝导致的气候驱动的分布范围收缩。
