Adelie penguin reproduction success, 1991-2021

The fundamental long-term objective of the seabird component of the Palmer LTER (PAL) has been to identify and understand the mechanistic processes that regulate the mean fitness (population growth rate) of regional penguin populations. Two hypotheses have guided this research, with one suggesting that population mean fitness is best explained by changes in regional krill biomass, and the other proposing that long-term changes in sea ice affects mean fitness by tipping the balance in favor of one species over another in accordance with species-specific evolved life history affinities to sea ice. Although these hypotheses are not mutually exclusive, current evidence in the PAL region tends to favor the latter over the former. Since the inception of PAL, Adélie penguin populations have effectively collapsed, while those of gentoo and chinstrap penguins have increased dramatically, trends that are spatially and temporally coherent with decreasing regional sea ice duration. Adélie penguins are an ice-obligate polar species whose life history is intimately linked to the presence of sea ice, while chinstrap and gentoo penguins are ice-intolerant species whose life histories evolved in the sub-Antarctic, where sea ice is a less permanent feature of the marine ecosystem. In contrast, although krill constitute the most important component of the summer diets by mass of these three penguin species, changes in PAL krill abundances have exhibited no long-term trends, and thus fail to explain the divergent patterns in penguin populations evident in our time series. A sample of Adélie penguin nests from colonies on Humble Island is randomly selected annually and checked daily (or as ice and weather conditions permit) throughout the breeding season from the time adults arrive until the chick crèche phase of the reproductive cycle. Recorded data (the timing of egg laying, hatching and crèching) provide a measure of annual breeding chronology, and the number of chicks crèched, an estimate of reproductive success (chicks crèched/breeding pair). Dr. Megan Cimino took over as PI of the LTER seabird project in 2020 from Dr. William Fraser. Field data collection between 2020-2022 has remained consistent with previous years. No lay dates were recorded during the 2020-2021 season due to a late start to the field season. No data collected during the 2021-2022 season due to the Palmer Station Pier Build.

帕尔默长期生态研究计划（Palmer LTER, PAL）的海鸟研究组分的核心长期目标，始终致力于识别并阐明调控区域企鹅种群平均适合度（种群增长率）的机制过程。本研究依托两项假说展开：其一认为种群平均适合度最佳可由区域磷虾生物量的变化解释；其二提出海冰的长期变化会通过改变物种间的生存平衡来影响平均适合度——即依据各物种对海冰演化出的专属生活史亲和性，使生存优势偏向某一物种。尽管两项假说并非互斥，但帕尔默长期生态研究区域的现有证据更倾向于后者。
自该计划启动以来，阿德利企鹅（Adélie penguin）种群已出现实质性衰退，而巴布亚企鹅（gentoo penguin）与帽带企鹅（chinstrap penguin）的种群数量则大幅增长；这些趋势与区域海冰存续时长缩短的时空特征高度一致。阿德利企鹅属于依赖海冰的极地物种，其生活史与海冰的存在紧密关联；而巴布亚企鹅与帽带企鹅则为不耐海冰的物种，其生活史演化于亚南极海域——该区域的海冰并非海洋生态系统中的永久性特征。
与之形成对比的是，尽管磷虾按生物量计是这三种企鹅夏季日粮中最重要的组成部分，但帕尔默长期生态研究区域的磷虾丰度并未呈现长期变化趋势，因此无法解释时间序列中观测到的企鹅种群分化模式。
每年会随机选取谦逊岛（Humble Island）上各企鹅群落的阿德利企鹅巢穴，在整个繁殖季（从成鸟抵达直至繁殖周期的雏鸟育幼群阶段）每日（或受海冰与天气条件允许时）开展监测。记录的数据包括产卵时间、孵化时间与雏鸟群聚时间，以此衡量年度繁殖物候；同时统计雏鸟群聚数量，以此估算繁殖成功率（雏鸟群聚数/繁殖对数量）。
梅根·西米诺（Megan Cimino）博士于2020年接替威廉·弗雷泽（William Fraser）博士，出任该海鸟研究项目的首席研究员（Principal Investigator, PI）。2020至2022年间的野外数据采集工作与此前年份保持一致，但受野外季启动延迟影响，2020-2021季未记录产卵日期；而2021-2022季因帕尔默站码头建设项目，未开展任何数据采集工作。