Management of colonial waterbirds at regional, national, and continental scales requires up-to-date monitoring information on breeding locations, population sizes, and trends. The large lakes of southern Manitoba, Canada (Winnipeg, Winnipegosis, and Manitoba), and the inter-lake region host nationally and continentally significant populations of colonial waterbirds, but the area has been surveyed only irregularly in the past. We conducted surveys in 2017 to produce updated information on population abundance and trends for the six most abundant species breeding on the lakes: Ring-billed Gull (Larus delawarensis), Herring Gull (Larus argentatus), Caspian Tern (Hydroprogne caspia), Common Tern (Sterna hirundo), Double-crested Cormorant (Phalacrocorax auritus), and American White Pelican (Pelecanus erythrorhynchos). We also examined the relationship between lake water levels and breeding pair abundance on Lake Winnipegosis. All species but American White Pelicans showed declines in recent years, and most notably populations of Caspian Tern and Common Tern were as low as or only just above 1970s levels, respectively. Higher water levels were associated with fewer breeding pairs of colonial waterbirds. The effects of water regulation in this region on colonial waterbirds and their habitat warrants further research, as does the degree to which the species use smaller lakes spread throughout the western boreal forest for breeding, especially during high water years on the lakes in southern Manitoba.

中文翻译：

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曼尼托巴省南部五个地区六种殖民地水鸟物种的丰度，人口趋势以及与湖水水平的负相关

在区域，国家和大陆范围内管理殖民地水鸟需要有关繁殖地点，种群数量和趋势的最新监测信息。加拿大曼尼托巴省南部的大湖（温尼伯，温尼伯西斯病和曼尼托巴省）以及湖间地区拥有全国和大陆上大量的殖民地水鸟种群，但过去仅对该地区进行了不定期调查。我们在2017年进行了调查，以提供有关湖上六个最丰富物种繁殖的种群数量和趋势的最新信息：环嘴鸥（Larus delawarensis），鲱鸥（Larus argentatus），里海燕鸥（Hydroprogne caspia），普通燕鸥（Sterna hirundo），双冠Cor（Phalacrocorax auritus）和美国白鹈鹕（Pelecanus erythrorhynchos）。我们还研究了温尼伯西斯湖上湖水位与繁殖对丰度之间的关系。近年来，除美洲白鹈鹕以外的所有物种均呈下降趋势，最值得注意的是里海燕鸥和普通燕鸥的种群数量分别低至或仅略高于1970年代。较高的水位与较少的殖民地水鸟繁殖对有关。该地区的水调节作用对殖民地水鸟及其栖息地的影响值得进一步研究，该物种使用较小湖泊的程度在整个北方寒带森林中繁殖，特别是在曼尼托巴省南部湖泊水位高涨期间。最值得注意的是里海燕鸥和普通燕鸥的数量分别低至或仅略高于1970年代。较高的水位与较少的殖民地水鸟繁殖对有关。该地区的水调节作用对殖民地水鸟及其栖息地的影响值得进一步研究，该物种使用较小湖泊的程度在整个北方寒带森林中繁殖，特别是在曼尼托巴省南部湖泊水位高涨期间。最值得注意的是里海燕鸥和普通燕鸥的数量分别低至或仅略高于1970年代。较高的水位与较少的殖民地水鸟繁殖对有关。该地区的水调节作用对殖民地水鸟及其栖息地的影响值得进一步研究，该物种使用较小湖泊的程度在整个北方寒带森林中繁殖，特别是在曼尼托巴省南部湖泊水位高涨期间。