Sarpong Keneth, Madliger Christine L, Harris Christopher M, Love Oliver P, Doucet Stéphanie M, Bitton Pierre-Paul
Department of Biological Sciences, University of Windsor, Windsor, Ontario N9B 3P4, Canada.
Gen Comp Endocrinol. 2019 Jan 1;270:123-130. doi: 10.1016/j.ygcen.2018.10.015. Epub 2018 Oct 28.
The production of high quality secondary sexual traits can be constrained by trade-offs in the allocation of energy and nutrients with other metabolic activities, and is mediated by physiological processes. In birds, the factors influencing male plumage quality have been well studied; however, factors affecting female plumage quality are poorly understood. Furthermore, it remains uncertain which physiological traits mediate the relationship between body condition and ornaments. In this three-year study of after-second-year female tree swallows (Tachycineta bicolor), we investigated (1) the relationship between baseline corticosterone near the end of the brood-rearing period (CORT) and feather colour characteristics (hue, saturation, brightness) the following year, and (2) the relationship between baseline corticosterone measured during incubation (CORT) and brood rearing (CORT), and feather colour in the same year. To control for reproductive effort, we included reproductive parameters as covariates in all analyses. In this first study between CORT and the plumage colour characteristics of a species bearing iridescent feathers, we did not find any relationship between CORT and the colour of subsequently-produced feathers, nor did we find any relationship between CORT and the colour of feathers displayed during that breeding season. If CORT levels at the end of breeding carry over to influence the immediately subsequent moult period as we expect, our results generally indicate that structural plumage quality may not be as sensitive to circulating CORT levels compared to carotenoid-based colouration. Future studies, particularly those employing experimental manipulations of CORT during moult in species with iridescent traits, are necessary to fully determine the role glucocorticoids play in mediating the quality of secondary sexual characteristics.
高质量第二性征的产生可能会受到能量和营养分配与其他代谢活动之间权衡的限制，并由生理过程介导。在鸟类中，影响雄性羽毛质量的因素已得到充分研究；然而，影响雌性羽毛质量的因素却知之甚少。此外，尚不确定哪些生理特征介导了身体状况与装饰之间的关系。在这项对两岁以上雌性树燕（双色树燕）进行的为期三年的研究中，我们调查了：（1）育雏期结束时的基础皮质酮水平（CORT）与次年羽毛颜色特征（色调、饱和度、亮度）之间的关系；（2）孵化期（CORT）和育雏期测量的基础皮质酮水平（CORT）与同年羽毛颜色之间的关系。为了控制繁殖投入，我们在所有分析中都将繁殖参数作为协变量纳入。在这项关于CORT与具有虹彩羽毛物种的羽毛颜色特征之间的首次研究中，我们没有发现CORT与随后产生的羽毛颜色之间存在任何关系，也没有发现CORT与该繁殖季节展示的羽毛颜色之间存在任何关系。如果繁殖结束时的CORT水平如我们所预期的那样会延续影响紧接着的换羽期，我们的结果总体表明，与基于类胡萝卜素的羽色相比，结构性羽毛质量可能对循环CORT水平不太敏感。未来的研究，特别是那些在具有虹彩特征的物种换羽期间对CORT进行实验性操纵的研究，对于全面确定糖皮质激素在介导第二性征质量方面所起的作用是必要的。
