Data from: Macronutrient selection of free-ranging urban Australian white ibis (Threskiornis moluccus)

Anthropogenic habitats often provide urban wildlife the opportunity to feed on a range of nutritionally diverse foods, which may ultimately lead to human-wildlife conflict. The Australian white ibis (Threskiornis moluccus) provides an exemplar model for examining the nutritional priorities and constraints of a native vertebrate that is successfully transitioning to an urban specialist. Here, we used field-based feeding trials to investigate the macronutrient preferences of free-ranging ibis in Sydney, Australia. Feeding trials (n = 61) offering three experimental feeds showed that ibis selected significantly more high-carbohydrate (HC) than high-protein (HP) and high-lipid (HL) foods (95% CIHP-HC = -1.115 to -0.709; CIHL-HC = -1.874 to -1.468), and significantly more HP than HL (CIHL-HP = -0.962 to -0.556). The average proportion of macronutrient-derived energy selected by ibis was 25% protein (P; ± 1.1 SE): 23% lipid (L; ± 1.1): 52% carbohydrate (C; ± 1.8). Nutritional geometry suggested that mixtures selected at experimental feeders were substantially higher in C and lower in P than are natural prey (e.g. insects, crustaceans), which were composed primarily of P and L. Compositional log-ratio-based linear models of factors affecting macronutrient proportions selected by ibis showed that: 1) ln(P/C) increased with amount of recent rainfall; and 2) ln(L/C) also increased with rain and had a non-linear relationship with number of birds feeding. Our results suggest that ibis forage for macronutrients rather than energy per se, and that their urban foraging is influenced by competition and the environment.人为栖息地通常可为城市野生动物提供取食多种营养丰富食物的机会，最终可能引发人兽冲突。澳洲白鹮（Threskiornis moluccus）是研究成功适应城市环境的本土脊椎动物的营养偏好与限制因素的典范模型物种。本研究于澳大利亚悉尼开展野外喂食实验，探究自由活动的澳洲白鹮的宏量营养素（macronutrient）偏好。本研究共设置61组喂食实验，提供三种实验饵料，结果显示：澳洲白鹮对高碳水化合物（high-carbohydrate, HC）饵料的取食选择显著多于高蛋白（high-protein, HP）与高脂（high-lipid, HL）饵料（95%置信区间CI_HP-HC为-1.115至-0.709，CI_HL-HC为-1.874至-1.468），同时其对HP饵料的取食选择也显著多于HL饵料（CI_HL-HP为-0.962至-0.556）。澳洲白鹮选取的宏量营养素来源能量占比均值为：蛋白质（P）25%（±1.1标准误）、脂质（L）23%（±1.1）、碳水化合物（C）52%（±1.8）。营养几何学（Nutritional geometry）分析表明，喂食器中白鹮选取的饵料混合物的碳水化合物占比显著高于天然猎物（如昆虫、甲壳类），而蛋白质占比更低——天然猎物主要由蛋白质与脂质构成。基于成分对数比的线性模型对影响澳洲白鹮选取宏量营养素比例的因素分析显示：1）ln(P/C)随近期降雨量增加而升高；2）ln(L/C)同样随降雨量增加而升高，且与取食鸟类数量呈非线性关系。本研究结果表明，澳洲白鹮的觅食行为以宏量营养素为目标而非单纯追求能量摄入，其城市觅食活动受到种间竞争与环境因素的共同影响。