SummaryThis research evaluated the nesting habitat, nest-site preferences, and nest architecture of the critically endangered White-bellied Heron Ardea insignis in Bhutan. There are fewer than 60 wild birds left in the world, distributed in Bhutan, India, and Myanmar with fewer than five active breeding pairs in Bhutan. From 2003 to 2018, 20 successful and two unsuccessful nests were located from which at least 76 juveniles were expected to have fledged. The population in Bhutan has remained at 22–30 individuals for the last decade. Site-specific data were collected from 22 nests, and additional vegetation and environmental data were collected from 14 nests and random sites. We used 20-m diameter circular plots to evaluate the site preferences. Ground vegetation, litter and rock cover were evaluated using four 1-m2 quadrats in both nest and random sites. Nesting habitat was analysed to compare characteristics of nesting sites to random sites. Our results suggest that the White-bellied Heron builds a simple platform nest within average distance of 74 m from water bodies on the tallest isolated trees at an average height of 18.3 m on an elevated site with a clear overview of surroundings and are sensitive to even slight disturbance. Our results also suggest that the bird has a preference for an east-facing aspect at an average slope of approximately 40° between the altitudes of 400–1,450 m. Our observations also suggest that the bird has abandoned all nesting sites used prior to 2015, and the frequency of nest re-use has decreased. Protecting each nest site from hazards, avoiding disturbance, maintaining safe feeding habitats and flight routes are essential to ensure continued breeding in current sites and survival of this population. Further research to better understand the habitat requirements for the White-bellied Heron is vital.

中文翻译：

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评估不丹极度濒危的白腹鹭Ardea insignis的巢栖息地、地点偏好和结构

总结这项研究评估了极度濒危的白腹苍鹭的筑巢栖息地、筑巢地点偏好和筑巢结构黄花梨在不丹。世界上只剩下不到60只野生鸟类，分布在不丹、印度和缅甸，不丹活跃的繁殖对不到5对。从 2003 年到 2018 年，发现了 20 个成功的巢穴和两个不成功的巢穴，预计至少有 76 只幼鸟从中成长。在过去十年中，不丹的人口一直保持在 22-30 人。从 22 个巢穴中收集了特定地点的数据，并从 14 个巢穴和随机地点收集了额外的植被和环境数据。我们使用 20 米直径的圆形地块来评估场地偏好。地面植被、垃圾和岩石覆盖使用四个 1-m2巢和随机地点的样方。对筑巢栖息地进行了分析，以将筑巢地点的特征与随机地点进行比较。我们的研究结果表明，白腹苍鹭在平均高度为 18.3 m 的高架场地上，在距水体 74 m 的平均距离内建造了一个简单的平台巢穴，对周围环境有清晰的认识，甚至对环境也很敏感。轻微的干扰。我们的研究结果还表明，这种鸟更喜欢在 400-1,450 m 的高度之间平均倾斜约 40° 的朝东方向。我们的观察还表明，这只鸟已经放弃了 2015 年之前使用的所有筑巢地点，并且重复使用巢穴的频率有所下降。保护每个巢穴免受危害，避免干扰，维持安全的饲养栖息地和飞行路线对于确保在当前地点继续繁殖和该种群的生存至关重要。进一步研究以更好地了解白腹苍鹭的栖息地要求至关重要。