The Attwater's prairie‐chicken (APC; Tympanuchus cupido attwateri) was listed as an endangered species in 1967, and since then multiple studies have addressed ecological and human factors that may have limited their population recovery. In this study, we used stable isotopes of carbon and nitrogen (δ¹³C and δ¹⁵N) in conjunction with Bayesian mixing models to determine current diets of APCs at the Attwater Prairie Chicken National Wildlife Refuge (APCNWR), and to compare them with past diets derived from the isotopic composition of feathers from museum specimens (1894–1965) to help elucidate potential factors limiting APC recovery. We collected feathers, blood, and feces from APCs at the APCNWR, and feathers from museum specimens. In addition, potential food items (vegetation, spiders, and insects) were collected from APCNWR and analyzed for δ¹³C and δ¹⁵N. A stable isotope mixing model (MixSIAR) was used to determine diet source contribution to past and present APC populations. δ¹³C values in APC blood were significantly greater in the fall than in the summer. Blood δ¹⁵N values were significantly greater in the summer than in the winter. δ¹³C values in feathers from museum and contemporary APCs were not different, although δ¹³C values in contemporary feathers were enriched by 0.5‰ relative to museum specimens. Results indicated that insects were the predominant food source in the summer and fall (61–65%) and C₃ vegetation was predominant in the winter (64%). Using isotope values from feathers, the model predicted that the predominant food source during the period of feather growth were insects (62%) followed by C₃ plants (17–18%), spiders (12–18%), and C₄ plants (2–3%). Feathers from contemporary birds had δ¹⁵N values 0.9‰ lower than those from museum specimens, suggesting potential shifts in diets in APCs currently in the wild relative to the past. We hypothesize that the abundance and species richness of various arthropods may have changed at the APCNWR resulting in current APCs in the wild feeding on arthropods with lower δ¹⁵N values than in the past. Orthopterans comprised about 23% of the APCs diet currently in the wild, while they represented only about 19% in the past.

中文翻译：

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得克萨斯州濒临灭绝的阿特沃特草原鸡的饮食来源：δ13C，δ15N和贝叶斯混合模型的证据

Attwater的草原鸡（APC; Tympanuchus cupido attwateri）在1967年被列为濒危物种，此后进行了多项研究，探讨了可能限制其种群恢复的生态和人为因素。在这项研究中，我们使用的碳和氮（的稳定同位素δ ¹³ C和δ ¹⁵N）与贝叶斯混合模型一起确定Attwater草原鸡国家野生动物保护区（APCNWR）的APC当前饮食，并将其与过去从博物馆标本的羽毛的同位素组成中提取的饮食进行比较（1894-1965年），以帮助阐明限制APC恢复的潜在因素。我们从APCNWR的APC收集了羽毛，血液和粪便，并从博物馆标本中收集了羽毛。此外，潜在的食物（植被，蜘蛛和昆虫）从APCNWR收集和分析δ ¹³ C和δ ¹⁵ N的稳定同位素混合模型（MixSIAR）被用来确定到过去和现在的APC群体饮食源贡献。δ ¹³秋季，APC血液中的C值明显高于夏季。血δ ¹⁵的N值是在夏天比冬天显著更大。δ ¹³在从博物馆和当代的APCs羽毛C值差异不显着，虽然δ ^13个在当代羽毛C值由0.5‰相对于博物馆标本富集。结果表明，昆虫是夏季和秋季的主要食物来源（61-65％），而C ₃植被在冬季是主要食物来源（64％）。使用羽毛的同位素值，该模型预测，羽毛生长期间的主要食物来源是昆虫（62％），其次是C ₃植物（17–18％），蜘蛛（12–18％）和C ₄植物（2-3％）。从现代鸟类的羽毛有δ ¹⁵比那些从博物馆标本的N值0.9‰降低，提示在装甲运兵车在日粮中的电位偏移目前在野外相对于过去。我们假设丰度，物种多样性以及各种节肢动物可导致节肢动物野生饲养当前的APC低δ的APCNWR已经改变了¹⁵比以往的N值。直翅目动物目前占野外APC饮食的23％，而过去仅占19％。