Data from: Male stress response is related to ornamentation but not resistance to oxidative stress in a warbler

1. Ornaments are thought to honestly signal individual quality to
potential mates. Individual quality may include the ability to cope with
stress through the production of glucocorticoids (GCs), which help to
redirect resources from growth or reproduction to survival during an acute
stress response. However, elevated levels of GCs may also increase
oxidative stress and reduce immune function. Thus, an important question
is whether high quality individuals, with more elaborate ornaments, signal
their ability to produce a strong stress response and mitigate some of the
negative effects of doing so through higher resistance to oxidative
stress. 2. We tested whether ornamentation and resistance to oxidative
stress were related to the magnitude of the increase in corticosterone
(CORT), the main GC in birds, during an acute stress response in common
yellowthroats (Geothlypis trichas). Males in this species have two plumage
ornaments, a black (eumelanin-based) facial mask and a yellow
(carotenoid-based) bib. We measured the increase in CORT in response to
capture and handling. 3. Males with more elaborate ornaments (larger masks
and more colourful bibs) had a greater increase in CORT during an acute
stress response. However, the increase in CORT was not related to
resistance to oxidative stress. 4. These results suggest that both
melanin- and carotenoid-based plumage ornaments can signal the ability of
a male to cope with stressors through a greater increase in CORT. Thus,
the association between ornamentation and stress induced CORT is not
likely due to a mechanism specific to a particular colour (melanin or
carotenoid), but instead may result from more general interactions between
CORT and health or condition.

1. 饰羽被认为可向潜在配偶诚实传递个体质量信号。个体质量可涵盖通过分泌糖皮质激素（glucocorticoids, GCs）应对应激的能力——在急性应激反应期间，该激素可帮助将资源从生长或繁殖转向生存保障。然而，糖皮质激素水平升高也可能加剧氧化应激并削弱免疫功能。因此，一个核心科学问题在于：拥有更精美饰羽的高质量个体，是否可通过更强的抗氧化应激能力，传递其能够产生较强应激反应并缓解该反应部分负面影响的信号？
2. 本研究以黄喉地莺（Geothlypis trichas）为研究对象，探究其在急性应激反应过程中，羽饰特征与抗氧化应激能力是否与鸟类主要糖皮质激素皮质酮（corticosterone, CORT）的升高幅度相关。该物种雄性具有两类羽饰：基于真黑素合成的黑色面部黑斑，以及基于类胡萝卜素合成的黄色喉斑。研究人员通过捕获与人工处置的方式，测定了个体皮质酮水平的升高幅度。
3. 饰羽更精美的雄性（黑斑面积更大、喉斑色彩更浓郁），在急性应激反应期间的皮质酮升高幅度更高。但皮质酮水平的升高幅度与抗氧化应激能力并无关联。
4. 上述结果表明，基于真黑素与类胡萝卜素合成的羽饰，均可通过更高幅度的皮质酮升高，传递雄性应对应激源的能力。因此，羽饰特征与应激诱导的皮质酮水平变化之间的关联，并非由特定色素（真黑素或类胡萝卜素）相关的机制介导，而是可能源于皮质酮与健康状态或身体状况之间更为普遍的相互作用。