Collaborative Research: Interactive Effects of Stress and Nutrition on Reproduction in Birds

合作研究：应激和营养对鸟类繁殖的相互作用stephen J. Schoech & & Reed bowman孟菲斯大学Archbold生物站正确的繁殖时间对动物最大限度地提高其适应性至关重要。为了在有利于生存的条件下繁殖后代，大多数生物依赖于各种环境线索。pi结合了观察和实验研究来证明食物的数量和质量影响育种的时间。在阿奇博尔德生物站（ABS）附近的野外生境中，生活在可自由获取人类食物的佛罗里达灌丛松鸦（Aphelocoma coerulescens）的繁殖时间总是比野生生境中的松鸦早。在野外，补充脂肪和蛋白质含量不同的饲料证实，这些营养物质协同作用，促进育种。饲喂高脂肪/高蛋白饲粮的雏鸟比对照组产蛋早，饲喂高脂肪/低蛋白饲粮的雏鸟产蛋多，后代存活率高。此外，研究人员还发现，与对照组相比，添加hfhp的成虫的越冬存活率有明显提高的趋势（尽管只在1月至3月添加了hfhp）。重要的是，郊区和HFHP野生松鸦的皮质酮（CORT）水平也低于野生对照。CORT是鸟类应激激素。由于CORT可以对生殖轴产生负面影响，因此CORT与营养之间的联系表明了生殖开始的独特机制。pi开发了一个新的模型，展示了资源如何影响压力（CORT），而压力反过来又影响育种的时机。与其他模型不同的是，该模型既预测了繁殖时间的提前，又预测了年际变化的减少——这与经验观察相一致。在繁殖季节的早期，鸟类可能会因食物供应减少而感到压力。尽管它们可能受到其他因素的“繁殖启动”，比如光周期，但高水平的CORT抑制了繁殖。但随着食物变得更可预测或质量更好，压力水平降低，抑制释放，允许繁殖发生。实地和圈养研究将用于检验这样一种假设，即与资源质量和/或可预测性有关的压力是环境线索转化为生殖决定的生理机制。郊区和hfhp补充的松鸦将被植入CORT，以确定它是否会延迟获得自由食物的雌性的繁殖。为了了解去除CORT是否会导致生殖轴的早期激活和提前产卵，将在ABS未补充CORT的松鸡中阻断CORT。PIs还将通过检查饮食，压力和繁殖时间对蛋大小，后代发育和短期和长期存活率的相互作用来评估资源可用性的最终影响。通过对蓝鸦的圈养研究，pi将进一步研究饮食与压力和繁殖之间的相互作用。这些研究允许对食物处理后的内分泌反应进行连续取样。pi将比较食物可预测性不同的松鸦的生殖激素和应激激素。此外，郊区夜间的光照可能会刺激生殖轴。这将通过比较在每日周期的黑暗阶段暴露在低水平光线下的松鸦和不暴露在低水平光线下的松鸦的一系列生理参数来进行测试。在自由生活的鸟类中，压力、环境资源和繁殖之间的相互作用尚未得到彻底的研究，这可能对鸟类如何选择繁殖时间至关重要。郊区部分强调了与全球城市化模式相关的快速环境变化如何影响自然选择的系统，并说明了潜在的后果。佛罗里达灌丛松鸦是一种日益减少的物种，它可以作为一个重要的模型，为许多分类群中越来越多的其他物种提供参考，这些物种正在或将面临类似的挑战，因为面对人类日益增加的使用，栖息地不断丧失。这个项目将在多个层面上带来好处。首先，佛罗里达灌木松鸦是一种濒危物种，这项研究可能提供减缓数量下降的方法。其次，收集到的技术和信息可以用来改善其他物种的衰退。第三，压力对生物体（包括人类！）健康的许多方面都有深远的负面影响，本研究（及相关项目）将考虑压力、营养、繁殖、免疫功能和生存之间的联系：所有这些都具有重要的跨物种影响。

Collaborative Research: Interactive Effects of Stress and Nutrition on Reproduction in BirdsStephan J. Schoech & Reed BowmanUniversity of Memphis & Archbold Biological StationCorrectly timing breeding is essential for animals to maximize their fitness. To produce young when conditions favor their survival, most organisms rely on a variety of environmental cues. The PIs have used a combination of observational and experimental studies to demonstrate that food quantity and quality influence timing of breeding. Florida Scrub-Jays (Aphelocoma coerulescens) in suburban habitats with access to ad libitum human-provided food always breed earlier than jays in wildland habitat at nearby Archbold Biological Station (ABS). In wildlands, supplementation with diets that differ in fat and protein content confirm that these nutrients act in synergy to advance breeding. Birds given high fat/high protein (HFHP) diets lay earlier than controls and jays supplemented with high fat/low protein diet, increase maternal allocation to eggs, and increase survival of offspring. Additionally, the PIs found a strong trend for increased over-winter survival of HFHP-supplemented adults relative to controls (even though birds are only supplemented from Jan-Mar). Importantly, both suburban and HFHP wildland jays also had lower levels of corticosterone (CORT), the avian stress hormone, than wildland controls. Because CORT can negatively affect the reproductive axis, the link between CORT and nutrition suggests a unique mechanism underlying the initiation of reproduction. The PIs have developed a novel model demonstrating how resources influence stress (CORT), which in turn influences timing of breeding. Unlike other models, this predicts both advanced timing of breeding and reduced between-year variation - consistent with empirical observations. Very early in the breeding season, birds may be stressed by reduced food availability. Although they may be "reproductively primed" by other cues, such as photoperiod, high levels of CORT inhibit reproduction. But as food become more predictable or of better quality, stress levels are reduced, releasing the inhibition, allowing breeding to occur. Field and captive studies will be used to test the hypothesis that stress associated with resource quality and/or predictability is the physiological mechanism by which environmental cues are translated into reproductive decisions. Suburban and HFHP-supplemented jays will be implanted with CORT to determine if it delays reproduction in females with access to ad libitum food. To learn whether the removal of CORT results in earlier activation of the reproductive axis and advanced laying, CORT will be blocked in unsupplemented jays at ABS. The PIs also will evaluate the ultimate effects of resource availability by examining the interactive effects of diet, stress, and time of breeding on egg size, offspring development, and short- and long-term survival. Using captive studies on Blue Jays, the PIs will examine further the interactions between diet and stress and reproduction. These studies allow serial sampling of endocrine responses to food treatments. The PIs will compare reproductive and stress hormones in jays that differ in the predictability in which food is provided. In addition, nocturnal light exposure in the suburbs may be stimulatory to the reproductive axis. This will be tested by comparing a suite of physiological parameters in jays that are exposed to low levels of light during the dark phase of the daily cycle with birds that are not. The interactions between stress, environmental resources, and reproduction have not been thoroughly investigated in free-living species and may be critical in how birds time reproduction. The suburban component underscores how rapid environmental change associated with global patterns of urbanization can influence naturally-selected systems, and illustrates the potential consequences. Florida Scrub-Jays are a declining species and may serve as an important model for an increasing number of other species from many taxa that are or will face similar challenges due to continued loss of habitat in the face of increasing human usage.This project will have benefits at multiple levels. First, Florida Scrub-Jays are a threatened species and this research may provide ways in which the decline in numbers may be slowed. Second, techniques and information gleaned may be used to ameliorate declines in other species. Third, stress has profound negative impacts upon many aspects of an organism's (humans included!) health, and this research (and associated projects) will consider links between stress, nutrition, reproduction, immune function, and survivorship: all of which have important cross-species implications.