Caspian terns (Hydroprogne caspia Pallas, 1770) present a sub-cosmopolitan but scattered distribution, and many of its colonies are in a vulnerable state. The species has been listed in the Red Data Book of the Russian Federation and is covered by the Agreement on the Conservation of African-Eurasian Migratory Waterbirds. We observed the colonies of Caspian terns repeatedly in the breeding season from May to June on the islands of Lake Chany from 1985 to 2011. We recorded clutch size, eggshell coloration and measured egg length and width to the nearest 0.1 mm with a caliper. Furthermore, we recorded the fate and hatching date of individual eggs and determined the clutch initiation date. Head, bill, tarsus length, and body weight of newly hatched chicks were measured. Caspian tern colony size changed between years from 50 nests in 1985 to 513 in 1999; therefore, the sample size of measured eggs varied from 90 to 1045. A total of 4137 eggs and 570 chicks were measured. We provide new information for this species nesting in west Siberia, which is important to compare with other local results. The presented data set is a novel long-term data set on an isolated population of this species in center of Eurasian continent. The complete data set for this abstract published in the Data Article section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023-02.1/jalter-en.

中文翻译：

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1985 年至 2011 年对俄罗斯西西伯利亚恰尼湖繁殖的里海燕鸥 (Hydroprogne caspia) 的蛋和雏鸟进行的长期系列测量

里海燕鸥 ( Hydroprogne caspiaPallas, 1770）呈现出亚国际化但分散的分布，其许多殖民地处于脆弱状态。该物种已被列入俄罗斯联邦红皮书，并受到《非洲-欧亚迁徙水鸟保护协定》的保护。1985年至2011年，我们在昌尼湖岛屿上的5月至6月繁殖季节反复观察了里海燕鸥的群体。我们记录了窝数、蛋壳颜色，并用卡尺测量了蛋的长度和宽度，精确到0.1毫米。此外，我们记录了各个蛋的命运和孵化日期，并确定了产卵开始日期。测量新孵出的雏鸡的头部、喙、跗节长度和体重。里海燕鸥群落规模逐年变化，从 1985 年的 50 个巢到 1999 年的 513 个；所以，测量鸡蛋的样本量从90个到1045个不等。总共测量了4137个鸡蛋和570只雏鸡。我们提供了有关该物种在西西伯利亚筑巢的新信息，这对于与其他当地结果进行比较非常重要。所提供的数据集是关于欧亚大陆中心该物种的一个孤立种群的新颖的长期数据集。发表在期刊数据文章部分的该摘要的完整数据集可在 JaLTER 中的 MetaCat 中以电子格式获取：http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023- 02.1/jalter-en。所提供的数据集是关于欧亚大陆中心该物种的一个孤立种群的新颖的长期数据集。发表在期刊数据文章部分的该摘要的完整数据集可在 JaLTER 中的 MetaCat 中以电子格式获取：http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023- 02.1/jalter-en。所提供的数据集是关于欧亚大陆中心该物种的一个孤立种群的新颖的长期数据集。发表在期刊数据文章部分的该摘要的完整数据集可在 JaLTER 中的 MetaCat 中以电子格式获取：http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023- 02.1/jalter-en。