Rosenfield Robert N, Hardin Madeline G, Bielefeldt John, Keyel Edward R
Department of Biology University of Wisconsin Stevens Point WI USA.
Ecol Evol. 2016 Dec 20;7(1):399-408. doi: 10.1002/ece3.2619. eCollection 2017 Jan.
Numerous studies have demonstrated earlier timing of spring migration and egg-laying in small passerines, but documentation of such responses to recent climate change in the life histories of higher trophic feeding birds such as raptors is relatively scarce. Raptors may be particularly susceptible to possible adverse effects of climate change due to their longer generation turnover times and lower reproductive capacity, which could lead to population declines because of an inability to match reproductive timing with optimal brood rearing conditions. Conversely adaptively favorable outcomes due to the influence of changing climate may occur. In general, birds that seasonally nest earlier typically have higher reproductive output compared to conspecifics that nest later in the season. Given the strong seasonal decline in reproductive output, and the heritability of nesting phenology, it is possible that nesting seasons would (adaptively) advance over time. Recent climate warming may release prior ecological constraints on birds that depend on food availability at the time of egg production, as do various raptors including Cooper's Hawks (). Under this scenario, productivity, especially clutch size, might increase because it is likely that this reproductive demographic may be the most immediate response to the earlier seasonal presence of food resources. We demonstrated a statistically significant shift of about 4-5 days to an earlier timing of egg-hatching in spring across 36 years during 1980-2015 for a partially migratory population of Cooper's Hawks in Wisconsin, United States, which is consistent with a recent study that showed that Cooper's Hawks had advanced their timing of spring migration during 1979-2012. Both studies occurred in the Great Lakes region, an area that compared to global averages is experiencing earlier and increased warming particularly in the spring in Wisconsin. The nesting period did not lengthen. We suggest that the gradual shift of six consecutive generations of hawks was likely in response to recent climate change or warming. We did not detect any long-term temporal change in average clutch or brood sizes. However, such indices of reproduction are among the highest known for the species and thus may be at their physio-ecological maximum for this population. Our study population appears to show resilience to and does not appear to be adversely influenced by the recent rate of changing climate at this time.
众多研究表明小型雀形目鸟类春季迁徙和产卵时间提前，但诸如猛禽等高营养级取食鸟类生活史中对近期气候变化的此类反应的记录相对较少。猛禽可能因其较长的世代更替时间和较低的繁殖能力而特别容易受到气候变化可能产生的不利影响，这可能导致种群数量下降，因为它们无法使繁殖时间与最佳育雏条件相匹配。相反，由于气候变化的影响，也可能会出现适应性有利的结果。一般来说，与在季节后期筑巢的同种鸟类相比，季节性筑巢较早的鸟类通常具有更高的繁殖产量。鉴于繁殖产量随季节大幅下降以及筑巢物候的遗传性，筑巢季节有可能（适应性地）随着时间推移而提前。近期的气候变暖可能会解除对依赖产卵时食物供应的鸟类（包括库珀鹰等各种猛禽）先前的生态限制。在这种情况下，生产力，尤其是窝卵数，可能会增加，因为这种繁殖种群数量可能是对季节性提前出现的食物资源最直接的反应。我们证明，1980年至2015年的36年间，美国威斯康星州部分迁徙的库珀鹰种群春季卵孵化时间在统计上显著提前了约4 - 5天，这与最近一项研究结果一致，该研究表明库珀鹰在1979年至2012年期间春季迁徙时间提前。这两项研究都发生在五大湖地区，与全球平均水平相比，该地区正经历更早且更剧烈的变暖，尤其是在威斯康星州的春季。筑巢期没有延长。我们认为连续六代鹰的逐渐变化很可能是对近期气候变化或变暖的反应。我们没有检测到平均窝卵数或育雏数的任何长期时间变化。然而，此类繁殖指标是该物种已知的最高指标之一，因此可能处于该种群生理生态的最大值。我们的研究种群似乎对近期气候变化速度具有恢复力，目前似乎未受到不利影响。
