黑嘴鸥（Larus saundersi）是世界濒危鸟类之一，中国鸟类红皮书中将其定为易危物种。自1871年在我国福建厦门收集到第一个标本以来，其生态学研究资料十分缺乏。1998-2008年，作者对中国境内黑嘴鸥繁殖期的日间活动规律、巢址时空变化、种群生存率、迁徙模式、遗传分化、种群动态等繁殖生态学进行了系统研究。同时，总结该物种的致危因素，提出了相应的保护管理对策。1. 黑嘴鸥巢址时空变化利用Arcview GIS对江苏盐城国家级自然保护区1999 -2007年，黑嘴鸥的巢址时空变化研究结果表明：区域尺度上，江苏盐城沿海黑嘴鸥种群数量维持在1000只左右，多年平均为954±161.26只，但由于滩涂围垦和开发，其营巢地主要集中在核心区，种群数量占整个种群数量的85.24%±7.00%。地点尺度上，中路港巢区的多年平均面积为153.19±112.09 hm2，三里闸巢区的多年平均面积为62.60±66.41 hm2；两个巢区的质心总体上均向东南方向偏移，中路港巢区与潮沟大泗洋子距离以及三里闸巢区与潮沟大流水距离均呈现减小趋势；但同一巢区，不同年份的重叠面积、密度和质心均不尽相同。年际间巢址的空间转换率较高（0.84±0.08，n=7 a）；但2007年由于碱蓬群落的退化导致其繁殖种群数量下降约40%。影响黑嘴鸥巢区时空变化的因素包括年际间降雨量、潮水的入侵、植被演替等自然因素，同时还包括无序开发利用滩涂生物资源、拾捡鸟蛋、人为改变滩涂水动力等人为因素。2. 黑嘴鸥的迁徙规律与生存率分析黑嘴鸥彩色旗标重见信息表明，辽宁种群可迁飞到其它3个地方种群的越冬地越冬，而韩国和山东种群仅迁飞到日本西部沿海越冬，江苏种群仅迁飞到我国东部沿海（包括台湾西部沿海）越冬。2006和2007年，辽宁双台河口幼鸟的生存率明显下降，可能与长期高密度利用同一个繁殖地有关。同时，采用国际广泛应用的MARK软件，得出黑嘴鸥亚成体的重见率（0.787-0.954）较成体（0.675-0.884）要高，黑嘴鸥亚成体的生存率（0.494-0.719）较成体要低（0.655-0.819）。3. 黑嘴鸥种群遗传结构与地理分化用分子生物学方法研究了黑嘴鸥种群的遗传结构和分化。对我国黑嘴鸥现存的3个地方种群50个样本的线粒体DNA控制区部分片段进行了序列测定，比对后所获得的550 bp的序列中，共发现48个变异位点，定义了34种线粒体单倍型，其中仅1种为我国3个地方种群间共享单倍型，多数为各地方种群内特有。我国3个地方种群内的单倍型多样性和核苷酸多态性都很高。结合已公布的的两个韩国样本的序列，4个地方种群合并成一个大种群时,其线粒体单倍型多样性与核苷酸多样性仍很高，分别为(0.974±0.012)％和(0.510±0.042)%。进一步分析表明，我国3个地方种群间核苷酸歧异度在0.433%–0.585%之间，种群分化程度FST在-0.03176–0.48063之间，基因流Nm在17.16–33.79之间，平均遗传距离为0.0051±0.0011。UPGMA系统发生树及最大简约网络图表明，黑嘴鸥的演化关系呈现星状辐射，单倍型之间呈现一种混杂的分布格局，地方种群没有形成明显的系统地理结构。4. 黑嘴鸥种群动态与栖息地变迁近10年的研究结果表明，中国境内黑嘴鸥繁殖种群数量呈增长趋势，但其繁殖依赖的碱蓬群落正面临退化、破碎化和消失的威胁。1992-2007年江苏盐城沿海15年间碱蓬群落减少79.1%（27358 hm2），主要转出为养殖塘，质心总体上向东南方向偏移。目前，仅梁跺河以南碱蓬滩涂存在扩展的可能，其余均处于消失和退化状态。黑嘴鸥的繁殖地由1992年的8处，减少到目前的2处，最直接和最主要原因是人工围垦导致适宜黑嘴鸥繁殖的碱蓬群落的消失。2001-2007年，山东黄河三角洲黑嘴鸥夏季种群数量和繁殖种群数量年际间波动较大，其年平均数量分别为483.14±250.53只（n=7 a）和只（n=7 a）。由于滩涂围垦，致使山东黄河三角洲黑嘴鸥的繁殖地趋向分布于黄河三角洲国家级自然保护区内，繁殖地的数量由1998年的7块，减少到2004-2005年的3块，2006年的4块，到2007又减少到3块，主要分布在大汶流管理站新黄河口滩涂以及湿地恢复区。1988-2005年辽宁双台河口国家级自然保护区17年间碱蓬群落减少79.73%（6791 hm2），主要转出为耕地和养殖塘，质心与黑嘴鸥繁殖栖息地分布基本一致，也逐渐向保护区西部转移。1996-2008年，黑嘴鸥繁殖种群数量呈增长趋势，年平均为3978.15±1734.64只（n=13 a）；繁殖地数量由1996年的13块减少到目前的3块，消失的主要原因为栖息地消失和外来种入侵。5. 黑嘴鸥的致危因素与保护对策通过1999-2008年的野外调查和研究证实IUCN（2001）公布的《红色名录等级和标准》中，将黑嘴鸥定为易危物种是正确的。研究表明石油开采、农业和水产品养殖业的发展，滩涂生物资源的利用，入侵物种和人为活动干扰是影响黑嘴鸥的主要威胁因子，建议从种群、栖息地和遗传三个方面，统筹规划和实施黑嘴鸥及其栖息地的保护。

Saunders’s Gull (Larus saundersi) is listed as a vulnerable species by IUCN and Birdlife International. This species is not nationally protected in China, although listed as vulnerable, due to a lack of available information. The species’ status and distribution has been unkown for over a century since its scientific discovery in Xiamen of Fujian, China in 1871. From 1998-2008, studies on daily activities, spatial-temporal variation of nest sites, population survival, migration patterns, genetic differentiation, and population dynamics of Saunders’s Gull were conducted in China. In addition, conservation and management measures were proposed based on our research results and findings, to address threat factors of this species and its habitats.1. Spatial-temporal variation in nesting sites of Saunders’s GullSpatial-temporal variations in nesting sites of Saunders’s Gulls at Yancheng National Nature Reserve were documented by applying GIS technology from 1999 to 2007. At regional level, a.k.a. Yancheng coastline, about 1000 Saunders’s Gulls (954±161.26) were recorded during this period. Due to land reclamation along the coastline, the gulls tended to nest more towards the core area of the reserve; nesting populations of Saunders’s Gulls in the core areas accounted for 85.24%±7.00% of the total population. At the site level within the coastline, mean area of nesting colonies were 153.19±112.09 hm2 in Zhonglugang and 62.60±66.41 hm2 in Sanlizha, respectively. Overlapping areas, density and centriod of nesting colonies for the same site were different among years; the centriods of different nesting colonies at the regional and local level tended to move southeast. Distances between nesting sites and tidal channels of Dasiyangzi and Daliushui decreased. The nest site spatial turnover rate was quite high (0.84±0.08, n=7 years) among years. Spatial-temporal variations in nesting areas of Saunders’s Gulls were caused by rainfall, tide, and vegetation succession, as well as human disturbances such as grass and clamworm harvesting and egg collection.2. Migration patterns and population survival estimates of Saunders’s GullResighting data of Saunders’s Gull indicated that the Liaoning sub-population migrates southwards and eastwards to wintering areas that also are used by three other sub-populations. The Shandong and S. Korea sub-populations migrate to the west coast of Japan. The Jiangsu sub-population migrates to the south coast of China (including the west coast of Taiwan Province). The fledging survival rates decreased in 2006 and 2007 in Liaoning, probably resulting from intensive use of a few shrimp ponds by a high nesting number of Saunders’s Gulls. Using the software MARK, we estimated that the average annual resighting rate is 0.787-0.954 for sub-adults and 0.675-0.884 for adults, and the survival rate is 0.494-0.719 for sub-adults and 0.655-0.819 for adult birds.3. Genetic structure and differentiation of Saunders’s GullA molecular method was used to reveal population genetic structure and differentiation of Saunders’s Gull. The mitochondrial control region (CR) sequence variation was assayed from 50 samples that were collected from three current breeding sites in China: Yancheng of Jiangsu, Yellow River Delta of Shandong, and Shuangtaihekou of Liaoning. A total of 48 variable sites were detected and 34 haplotypes were defined from the aligned 550 bp of the 5′ CR. Only 1 haplotype was shared by all three sub-populations in China and most of the haplotypes were unique to a sub-population. Diversity in hyplotypes and nucleotides was high within a population. With the addition of sequences of two South Korean samples obtained from the published literature, the overall diversity for the four sub-populations was considerably high ( h = 0.974% ± 0.012％, π= 0.510% ± 0.042%). The range of the nucleotide divergence, the pairwise FST, and the gene flow (Nm) among three populations in China were 0.457%–0.585%, -0.03176–0.48063, and 17.16–33.79 respectively. The mean genetic distance among the three sub-populations in China was 0.0051±0.0011. UPGMA tree and statistical parsimony cladogram showed a very shallow phylogenetic tree and a star-like haplotype network, indicating that no distinctive geographic phylogeography has occurred among the four sub-populations.4. Breeding population dynamics and habitat changeOver the past decade, the breeding population of Saunders’s Gull has been increasing in China. The Common Seepweed community on which Sanuder’s Gulls rely, however, is challenged with degradation, fragmentation, and loss.Between 1992 and 2007, the area of Common Seepweed community had decreased by 79.1% (27 358 hm2) in Yancheng NNR, predominantly as a result of conversion to aquaculture ponds and farmlands. Except in the south of Liangduo River, the Common Seepweed community in all other areas in the reserve had suffered degradation. The number of breeding sites decreased from eight in 1992 to two now in Yancheng NNR, suggesting that the conversion of Common Seepweed to other land uses is the major and direct cause of the loss of breeding habitats for Saunders’s Gull.The population of Saunders’s Gulls was unstable from 2001 to 2007 in the Yellow River Delta of Shandong Province. Annual average numbers of total and breeding population were 483.14±250.53 (n=7 years) and 350.29±272.12 (n=7 years) respectively during this period. Due to beach reclamation, the number of nesting sites reduced from seven in 1998 to three in 2008, and the gulls tended to breed more within the Yellow River Delta NNR, especially in the mudflats in the new estuary of the Yellow River and restored wetlands at Dawenliu Management Station.From 1988 to 2005, the area of the Common Seepweed community decreased by 79.73 % (or 6 791 hm2) in Shuangtaihekou NNR, predominantly due to conversion to farmlands and aquiculture ponds. The annual average breeding number of Saunders’s Gulls was 3978.15±1734.64 (n=13 years) from 1996-2008, with a trend of population increasing. The number of breeding sites, however, decreased from 13 in 1996 to three in 2008 in Shuangtaihekou NNR, indicating that conversion of Common Seepweed community to other land use and the invasion of exotic species are the main cause of the loss of breeding habitats for Saunders’s Gulls.5. Conservation and managementThe research results of Saunders’s Gull meets categories A3c, A3e, B2a, B2b, B2c and D2 as vulnerable issued by IUCN Red Data List in 2001. Our research, as well as previous studies, identified main threatening factors to this species, including human population growth, economic development (especially agriculture and aquaculture development), oil exploitation, biological resource use, human intrusions and disturbance, and invasive species. To deal with these threats, conservation and management measures for this species and its habitats were proposed with aspects of population, habitat and genetics.