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.

人为栖息地往往为城市野生动物提供了摄取各类营养多样食物的机会，这最终可能引发人兽冲突。澳洲白鹮（Threskiornis moluccus）为研究成功转型为城市特化物种的本土脊椎动物的营养偏好与限制条件提供了典范模型。本研究通过野外摄食实验，探究了澳大利亚悉尼市境内自由活动的澳洲白鹮的宏量营养素偏好。共开展61组摄食实验，设置三种实验饵料，结果显示：澳洲白鹮对高碳水化合物（HC）组饵料的选择量显著高于高蛋白（HP）与高脂肪（HL）组（95%置信区间HP-HC为-1.115至-0.709；CIHL-HC为-1.874至-1.468），且对HP组饵料的选择量也显著高于HL组（CIHL-HP为-0.962至-0.556）。澳洲白鹮所选宏量营养素的供能平均占比为：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（Nutritional Geometry）分析表明，实验投喂点所选饵料的营养组合中，碳水化合物占比显著高于天然猎物（如昆虫、甲壳类），而蛋白质占比则更低——天然猎物主要由蛋白质与脂质构成。基于组成对数比的线性模型对影响澳洲白鹮所选宏量营养素占比的因素分析显示：1）ln(P/C)随近期降雨量增加而升高；2）ln(L/C)同样随降雨量升高而增加，且与摄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，而非单纯以能量"per se"为导向，其城市觅食活动同时受种间竞争与环境因素的影响。