Isotopic niche segregation during the non-breeding period in Black-faced Cormorants (<i>Phalacrocorax fuscescens</i>)

Due to environmental changes, prey distribution and availability are predicted to change. This is expected to impact their predators, especially in the highly dynamic and fast-changing marine environment. To predict these impacts, knowledge of predator diets throughout the annual cycle is needed. During the breeding season, collecting diet samples from seabirds is relatively simple, but data on other periods are harder to obtain. To study trophic niche during the non-breeding period, stable isotopes extracted from feathers can be used as a proxy. Bulk stable isotope ratios of carbon (¹³C/¹²C), nitrogen (¹⁵N/¹⁴N) and sulphur (³⁴S/³²S) of feathers (<i>n</i> = 96), blood (<i>n</i> = 10) and gut content (<i>n</i> = 56) were combined with GPS tracking data (<i>n</i> = 30) to study the trophic niche, individual niche consistency and the link between non-breeding trophic niche and habitat use in Black-faced Cormorants (<i>Phalacrocorax fuscescens</i>). On the population level, a large range in isotope compositions (combination of C, N and S isotope ratios) was observed, indicating that individuals exploit diverse prey and habitats. However, comparing blood (breeding) and feather (non-breeding) stable isotope data from the same individuals revealed little within-individual variation in isotope compositions, indicating individual consistency in exploited prey or habitats. Tracking data revealed that δ¹³C, δ¹⁵N and δ³⁴S values in feathers reflected whether an individual foraged in shallow or deeper habitats during the non-breeding period and may be used to monitor habitat use. This study provides further insights into the year-round diet and foraging of the poorly studied Black-faced Cormorant.

受环境变化影响，猎物的分布与可获得性预计将发生改变，这势必会对其天敌种群造成冲击，在高度动态且变化迅速的海洋环境中尤为如此。为预测此类影响，需掌握捕食者全年的饮食组成信息。对于海鸟而言，繁殖季的饮食样本采集相对简便，但其他时段的数据则较难获取。为研究非繁殖期的营养生态位，可借助从羽毛中提取的稳定同位素作为替代指标。本研究以黑脸鸬鹚（*Phalacrocorax fuscescens*）为研究对象，整合了96份羽毛样本、10份血液样本与56份肠道内容物样本的碳（¹³C/¹²C）、氮（¹⁵N/¹⁴N）及硫（³⁴S/³²S）整体稳定同位素比值数据，并结合30份GPS追踪数据，旨在探究其营养生态位、个体生态位一致性，以及非繁殖期营养生态位与栖息地利用之间的关联。在种群尺度上，研究观测到同位素组成（碳、氮、硫同位素比值的组合）存在较大跨度，表明个体利用的猎物与栖息地具有多样性。然而，对比同一黑脸鸬鹚个体的血液（对应繁殖季）与羽毛（对应非繁殖季）稳定同位素数据后发现，个体内的同位素组成差异极小，这说明其在捕食猎物或利用栖息地方面存在个体一致性。追踪数据显示，羽毛中的δ¹³C、δ¹⁵N与δ³⁴S值能够反映个体在非繁殖期是否于浅海或深海生境觅食，因此可用于监测其栖息地利用情况。本研究进一步揭示了此前研究较少的黑脸鸬鹚全年饮食与觅食行为特征。

搜集汇总

背景与挑战

背景概述

该数据集聚焦于黑脸鸬鹚在非繁殖期的同位素生态位分离研究，通过分析羽毛、血液和肠道内容物的碳、氮、硫稳定同位素比率，结合GPS追踪数据，揭示了种群水平上个体利用多样猎物和栖息地的生态位多样性，同时发现个体在繁殖与非繁殖期间的同位素组成具有一致性，表明个体对猎物或栖息地的选择较为稳定。研究进一步探讨了同位素值与浅水或深水栖息地觅食行为的关联，为理解这一物种的全年饮食和觅食生态提供了新见解。