Asian hornbills are known to forage and breed in fragmented rainforests and agroforestry plantations in human‐modified landscapes adjoining contiguous protected forests. However, the factors influencing year‐round hornbill abundance, demography and tracking of key food resources such as wild fig Ficus fruits in modified habitats and protected forests remain poorly understood. We carried out monthly surveys of two species of high conservation concern, the Vulnerable Great Hornbill (GH, Buceros bicornis) and the endemic Malabar Grey Hornbill (MGH, Ocyceros griseus) for 15 months and monitored ripe fig fruit availability for 12 months along 11 line transects (total length 24 km) in shade‐coffee plantations and adjoining continuous rainforests in a protected area (PA) in the Anamalai Hills, Western Ghats, India. Both hornbill species used plantations and the PA year‐round but distance sampling density estimates were higher in the PA in both nesting (GH by 57%; MGH by 50%) and non‐nesting (GH by 53%; MGH by 144%) seasons. Relative to estimates from 2004 to 2005, mean GH density appeared stable or increasing, whereas MGH had declined by 39% in the PA and by 56% in plantations. Monthly encounter rate of both hornbills tended to be higher in the PA and that of MGH was also positively related to the density of fig trees with ripe fruit. Sex ratios of observed adult birds in the non‐nesting season were relatively even (GH) or slightly female‐biased (MGH), but became male‐biased in both species during the nesting season when females were confined in tree‐cavity nests. We used change in the adult sex ratio of observed birds from the non‐nesting to nesting season to estimate an index of the proportion of adult pairs breeding at any point within the season, providing the first such estimates for any hornbill species. The proportion of breeding pairs was higher in the PA (GH – 56%, MGH – 64%) than in the plantations (GH – 33%, MGH – 30%). Although hornbills use shade‐coffee plantations year‐round, partly due to fig fruit availability, differences in hornbill density and breeding incidence, as assessed from the sex ratios of observed adult birds, indicate that plantations are a sub‐optimal habitat for both species.

中文翻译：

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犀鸟的丰度和繁殖发生率与栖息地的改变和无花果的可利用性有关

众所周知，亚洲犀鸟在零碎的热带雨林和农林人工林中觅食和繁殖，这些人工林与毗邻的受保护森林相邻。然而，影响全年犀鸟丰富，人口和关键的粮食资源跟踪，如野生无花果的因素榕树果实修改栖息地和受保护的森林仍然知之甚少。我们每月对两种高度关注保护的物种进行调查，即脆弱的大犀鸟（GH，Buceros bicornis）和特有的马拉巴尔灰犀鸟（MGH，Ocyceros griseus））15个月，并在印度西高止山脉Anamalai Hills的一个保护区（PA）沿遮荫咖啡种植园和11个连续的雨林沿11个样线样（总长24 km）监测了12个月的成熟无花果果实可用性。两种犀鸟物种都使用人工林和全年的PA，但是在巢区（GH降低了57％； MGH降低了50％）和非嵌套（GH降低了53％； MGH降低了144％）时，PA的距离采样密度估计值都更高。季节。相对于2004年至2005年的估计值，平均GH密度似乎稳定或增加，而PA中的MGH下降了39％，人工林中的MGH下降了56％。在宾夕法尼亚州，两种犀鸟的月相交率趋于较高，而MGH的月相交率也与成熟果无花果树的密度呈正相关。在非嵌套季节观察到的成年鸟的性别比相对均匀（GH）或略有雌性偏向（MGH），但是在雌鸟被限制在树洞巢中的筑巢季节中，这两个物种的雄性都有偏见。我们使用了从非嵌套季节到筑巢季节观察到的鸟类成年性别比的变化，以估算该季节内任何时间点成年成对成对的比例的指数，从而首次对任何犀鸟物种进行了此类估算。PA中的育种对比例（GH – 56％，MGH – 64％）高于人工林（GH – 33％，MGH – 30％）。尽管犀鸟全年都使用遮荫咖啡种植园，部分原因是由于无花果果实的可利用性，犀鸟密度和繁殖发生率的差异（根据观察到的成年鸟的性别比例评估），