Isotopic signatures of foraging among adult Pygoscelis penguins nesting along the Palmer Archipelago near Palmer Station, 2007-2009

We evaluated regional variation in reproductive isotopic niche among breeding populations of Adélie (Pygoscelis adeliae), chinstrap (P. antarctica), and gentoo (P. papua) penguins west of the Antarctic Peninsula (AP) to test a hypothesis for sea ice-associated food-web correlates of breeding population change. We rely on signatures of naturally occurring carbon (13C/12C, δ13C) and nitrogen (15N/14N, δ15N) stable isotopes (SI) as integrated proxies of penguin trophic foraging and food-web structure. Each season, study nests, where pairs of adults were present, were individually marked and chosen before the onset of egg-laying, and consistently monitored. When study nests were found at the one-egg stage, both adults were captured to obtain blood samples used for molecular sexing and stable isotope analyses, and measurements of structural size and body mass. At the time of capture, each adult penguin was quickly blood sampled (~1 ml) from the brachial vein. After handling, individuals at study nests were further monitored to ensure the pair reached clutch completion, i.e., two eggs. At approximate an average nest age of five and 15 days, offspring from study nests were captured and quickly blood sampled (≤ ~500 μl for day five chicks, and ≤ ~1 ml for day 15 chicks) from the tarsus vein using a sterile needle and heparinized capillary tubes for day five chicks, and a sterile 3 ml syringe and heparinized infusion needle for day 15 chicks, again to obtain blood tissue for SI analyses. Study nests were monitored for chick survival to 25 days. At five weeks into chick-rearing, older crèched chicks of all three species were captured and quickly blood sampled from study rookeries near Anvers Island. Handling of crèched chicks occurred over a one or two day period, which varied seasonally and by species depending on nest initiation dates. Adélie penguin chicks at Avian Island were sampled on the same day Anvers Island Adélie penguin chicks were sampled. Adélie penguin chicks at Charcot Island, sampled during one season only on 25 January 2010, were handled three days after Anvers Island and Avian Island Adélie penguin chicks were sampled that year, i.e., 22 January 2010. Blood samples from crèched chicks (~1 ml) were taken from the brachial vein using a sterile 3 ml syringe and heparinized infusion needle following sampling procedures used for adult penguins to obtain blood tissue for SI analyses. Stable isotope analyses were conducted at the Stable Isotope Facility at the University of California, Davis using an elemental analyzer interfaced with an isotope ratio mass spectrometer

本研究针对南极半岛（Antarctic Peninsula, AP）西部的阿德利企鹅（Pygoscelis adeliae）、帽带企鹅（P. antarctica）与巴布亚企鹅（P. papua）的繁殖种群，评估其繁殖生态位的区域差异，以检验关于海冰关联食物网与繁殖种群变化相关性的假说。本研究利用天然存在的碳（¹³C/¹²C, δ¹³C）与氮（¹⁵N/¹⁴N, δ¹⁵N）稳定同位素（stable isotopes, SI）信号，作为企鹅营养觅食与食物网结构的综合替代指标。
每个繁殖季，研究人员于产卵前选定成对成鸟栖息的研究巢位，进行个体标记并开展持续监测。当发现研究巢位处于单枚卵阶段时，捕获两只成鸟以采集血液样本，用于分子性别鉴定、稳定同位素分析，并测量其体型与体质量。捕获时，从每只成鸟的臂静脉快速采集约1 mL血液样本。完成操作后，继续监测研究巢位的成鸟，确保其完成产卵（即产下两枚卵）。
当研究巢位的雏鸟平均日龄约为5天与15天时，分别捕获雏鸟并快速采集血液样本：5日龄雏鸟从跗跖静脉采集，使用无菌针头与肝素化毛细管，采血量不超过约500 μL；15日龄雏鸟则使用无菌3 mL注射器与肝素输液针头，采血量不超过约1 mL，样本用于稳定同位素分析。研究人员持续监测研究巢位的雏鸟至25日龄的存活情况。
雏鸟育雏至5周时，在安弗岛（Anvers Island）附近的研究繁殖群中捕获所有三个物种的集群雏鸟并快速采血。集群雏鸟的捕获采血工作持续1至2天，该时长随繁殖季与物种而异，取决于巢位的起始产卵时间。阿维安岛（Avian Island）的阿德利企鹅雏鸟与安弗岛的阿德利企鹅雏鸟于同日采样。沙科特岛（Charcot Island）的阿德利企鹅雏鸟仅在2010年一个繁殖季采样，采样日期为2010年1月25日，比当年安弗岛与阿维安岛的阿德利企鹅雏鸟采样时间晚3天，即2010年1月22日。
集群雏鸟的血液样本（约1 mL）采集自臂静脉，使用无菌3 mL注射器与肝素输液针头，遵循成鸟采样流程，样本用于稳定同位素分析。稳定同位素分析于美国加州大学戴维斯分校稳定同位素实验室完成，使用连接同位素比值质谱仪的元素分析仪进行检测。