Monitoring seabird diet can provide insights into marine ecosystems that are logistically difficult or costly to observe with traditional fisheries survey methods. Using digital photography, we described the diet of greater crested terns (Thalasseus bergii) breeding on Montague Island (36°15′ S, 150°13′ E), a colony located in an oceanographically dynamic region of southeast Australia. We investigated how the type and size of prey brought back to the colony changed in relation to both breeding stage and variation in local environmental conditions. 2469 prey items were identified to species or family level over 35 consecutive days of photo-sampling in 2018. Australian anchovy (Engraulis australis), a surface-schooling clupeid fish, was the most abundant prey returned to the colony during all breeding stages (84.5%). The proportion of anchovy increased from 77.0% when birds were provisioning their adult partners during incubation, to 92.4% when they were provisioning chicks, suggesting selective foraging behaviour on this energy-rich species to facilitate rapid chick growth. Anchovy size was significantly larger during incubation (91.1 ± 14.9 mm), smaller during early chick provisioning (71.8 ± 11.0 mm), and increased slightly during mid provisioning (79.6 ± 11.9 mm), indicating adaptive prey selection that is matched to the physical requirements of different breeding stages. The proportion of anchovy prey was also influenced by sea surface temperature (SST), with anchovy becoming more dominant with increasing local SSTs, up to ~ 17.5 °C. This study gives new insight into the types of prey that are seasonally available to predators in this region. The strong specialisation by greater crested terns for one energy-rich species of schooling fish (anchovy) suggests that variation in the size and composition of their prey may serve as an indicator of change in the pelagic ecosystem off southeast Australia.

监测海鸟饮食可以深入了解使用传统渔业调查方法在后勤上难以观察或成本高昂的海洋生态系统。使用数码摄影，我们描述了在蒙塔古岛（南纬 36 度 15 分，东经 150 度 13 分）上繁殖的大凤头燕鸥 ( Thalasseus bergii )的饮食，该岛位于澳大利亚东南部的海洋动态区域。我们调查了带回殖民地的猎物的类型和大小如何随着繁殖阶段和当地环境条件的变化而变化。在 2018 年连续 35 天的照片采样中，2469 件猎物被鉴定为物种或科系。)，一种在水面学习的鲇鱼，是在所有繁殖阶段返回群落的最丰富的猎物 (84.5%)。鳀鱼的比例从孵化期间鸟类供应成年伴侣时的 77.0% 增加到供应雏鸡时的 92.4%，表明这种富含能量的物种的选择性觅食行为促进了雏鸡的快速生长。孵化期间凤尾鱼的尺寸明显较大 (91.1 ± 14.9 毫米)，早期雏鸡供应期间较小 (71.8 ± 11.0 毫米)，中期供应期间略有增加 (79.6 ± 11.9 毫米)，表明与身体要求相匹配的适应性猎物选择不同的繁殖阶段。鳀鱼猎物的比例也受到海面温度 (SST) 的影响，随着当地 SST 的增加，鳀鱼变得更加占主导地位，高达 ~ 17.5 °C。这项研究为该地区捕食者季节性可用的猎物类型提供了新的见解。大凤头燕鸥对一种富含能量的鱼群（凤尾鱼）的强烈专业化表明，它们猎物的大小和组成的变化可能是澳大利亚东南部远洋生态系统变化的一个指标。