Whelan Shannon, Strickland Dan, Morand-Ferron Julie, Norris D Ryan
Department of Biology University of Ottawa Ottawa ON Canada.
1063 Oxtongue Lake Road Dwight ON Canada.
Ecol Evol. 2017 Mar 23;7(9):3029-3036. doi: 10.1002/ece3.2864. eCollection 2017 May.
Timing of reproduction can influence individual fitness whereby early breeders tend to have higher reproductive success than late breeders. However, the fitness consequences of timing of breeding may also be influenced by environmental conditions after the commencement of breeding. We tested whether ambient temperatures during the incubation and early nestling periods modulated the effect of laying date on brood size and dominant juvenile survival in gray jays (), a sedentary boreal species whose late winter nesting depends, in part, on caches of perishable food. Previous evidence has suggested that warmer temperatures degrade the quality of these food hoards, and we asked whether warmer ambient temperatures during the incubation and early nestling periods would be associated with smaller brood sizes and lower summer survival of dominant juveniles. We used 38 years of data from a range-edge population of gray jays in Algonquin Provincial Park, Ontario, where the population has declined over 50% since the study began. Consistent with the "hoard-rot" hypothesis, we found that cold temperatures during incubation were associated with larger brood sizes in later breeding attempts, but temperatures had little effect on brood size for females breeding early in the season. This is the first evidence that laying date and temperature during incubation interactively influence brood size in any bird species. We did not find evidence that ambient temperatures during the incubation period or early part of the nestling period influenced summer survival of dominant juveniles. Our findings provide evidence that warming temperatures are associated with some aspects of reduced reproductive performance in a species that is reliant on cold temperatures to store perishable food caches, some of which are later consumed during the reproductive period.
繁殖时间会影响个体适合度，早期繁殖者往往比晚期繁殖者具有更高的繁殖成功率。然而，繁殖时间对适合度的影响也可能受到繁殖开始后环境条件的影响。我们测试了孵化期和雏鸟早期的环境温度是否会调节产卵日期对灰噪鸦（一种定居的北方物种，其冬末筑巢部分依赖于易腐食物的储存）窝卵数和优势幼鸟存活率的影响。先前的证据表明，温度升高会降低这些食物储备的质量，我们想知道孵化期和雏鸟早期环境温度升高是否会与较小的窝卵数以及优势幼鸟较低的夏季存活率相关。我们使用了安大略省阿尔冈昆省立公园灰噪鸦边缘种群38年的数据，自研究开始以来，该种群数量已下降超过50%。与“贮藏腐烂”假说一致，我们发现孵化期的低温与后期繁殖尝试中较大的窝卵数相关，但温度对季节早期繁殖的雌鸟窝卵数影响不大。这是首次有证据表明，产卵日期和孵化期温度会交互影响任何鸟类的窝卵数。我们没有发现证据表明孵化期或雏鸟早期的环境温度会影响优势幼鸟的夏季存活率。我们的研究结果表明，对于一个依赖低温来储存易腐食物储备（其中一些在繁殖期后期被消耗）的物种，气温升高与繁殖性能下降的某些方面有关。
