There are few quantitative estimates of numbers of Africa's endangered grey crowned cranes (Balearica regulorum), yet conservation of this species will depend on such estimates. We used line‐transect distance sampling on multiple 2‐km segments of an existing road network to estimate the abundance of grey crowned cranes in a portion of the Ngorongoro Crater, Tanzania, during the wet (April) and dry (August) seasons of 2016. We analysed data from 106 transects on which we observed 174 groups of 1–61 cranes (median and mode = 2). Abundance and density estimates on the areas surveyed were best modelled without group size as a covariate and indicated that mean crane densities were significantly lower in the wet season (2.4/km²) than in the dry season (20.2 cranes/km²). Even based on survey areas of different size, minimum estimated numbers of cranes in the Crater (wet season: 108–133; dry season: 362–401) likely reflect the concentration of cranes in the nonbreeding (dry) season in the perennial wetlands of the Crater and reinforce the notion of the Crater being a key seasonal habitat for crane populations in northern Tanzania, as previously suggested in the literature.

中文翻译：

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坦桑尼亚Ngorongoro火山口的灰冠鹤（Balearica regulorum）丰度的季节性变化

对非洲濒临灭绝的灰冠鹤（Balearica regulorum）数量的定量估计很少，但是该物种的保护将取决于这种估计。我们在现有道路网的多个2 km段上使用线样线距离采样来估计2016年雨季（4月）和旱季（8月）坦桑尼亚Ngorongoro火山口的一部分中的灰顶鹤数量我们分析了106个样例的数据，在这些样例中我们观察了174组1-61台起重机（中位数和众数= 2）。在没有组大小的协变量的情况下，对被调查区域的丰度和密度估计最好进行建模，表明在雨季（2.4 / km ²），平均鹤密度明显低于旱季（20.2鹤/ km ^2）。）。即使基于不同规模的调查区域，火山口中起重机的最小估计数量（湿季：108–133；旱季：362–401）也可能反映了常年湿地非繁殖（干旱）季节中起重机的浓度。火山口，并强化火山口的概念，因为火山口是坦桑尼亚北部起重机种群的重要季节性栖息地，如先前文献所暗示的那样。