Eastern hemlock (Tsuga canadensis) is declining throughout the eastern United States due to hemlock woolly adelgid (Adelges tsugae Annand), an invasive insect from Asia. In the southern Appalachians, hemlock is concentrated in moist ravines and its decline threatens riparian ecosystems. Previous research on this invasion has focused on adelgid control and how hemlock decline affects community composition or forest processes; few studies have evaluated the consequences for demography of obligate riparian species. The Louisiana Waterthrush (Parkesia motacilla) is an obligate riparian species that could be sensitive to hemlock condition in this region, but how individuals respond to decline is currently unknown. To address this knowledge gap, we leveraged recent adelgid treatment efforts in Great Smoky Mountains National Park to evaluate the relationship(s) between hemlock decline and waterthrush habitat selection (foraging and nest site) and vital rates (nest and adult survival). We found that hemlock decline was unrelated to foraging habitat selection and apparent adult survival, but was related to nest site selection through an interaction with percent ground cover of exposed live tree roots: birds selected for nest sites in areas with more exposed live roots but only when hemlock was in poor condition. Nest survival was lower in areas where deciduous species (vs. evergreen species) dominated the understory, suggesting that adelgid invasion could indirectly impact waterthrush fitness depending on how vegetative succession proceeds following hemlock decline. Our results suggest that the short-term consequences of adelgid invasion on this riparian avian species are minimal in this area, but these relationships are likely dynamic and dependent on local habitat features and the predator community response to hemlock decline.

中文翻译：

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入侵性昆虫，铁杉羊毛阿德吉德，间接影响路易斯安那州南部阿巴拉契亚人的Waterthrush巢址选择和巢生存

东部铁杉（Tsuga canadensis）在全美国正在下降，这是由于铁杉毛adelgid（Adelges tsugae Annand）（一种来自亚洲的入侵昆虫）引起的。在阿巴拉契亚南部，铁杉集中在潮湿的山沟上，其下降威胁着河岸生态系统。先前有关这种入侵的研究集中在艾德吉德控制以及铁杉下降如何影响群落组成或森林进程方面。很少有研究评估专性河岸物种的人口统计学后果。路易斯安那州的水彩画（Parkesia motacilla）是专性河岸种，可能对该地区的铁杉状态敏感，但目前尚不清楚个体如何应对下降。为了解决这一知识鸿沟，我们利用最近在大烟山国家公园中进行的adelgid处理工作，来评估铁杉下降和水th栖息地选择（觅食和筑巢地点）与生命率（巢和成虫生存）之间的关系。我们发现铁杉下降与觅食栖息地选择和明显的成年存活无关，但与巢穴的选择通过与裸露的活树根的地面覆盖率的相互作用有关：选择鸟巢的地方是裸露的活根较多的地区，但仅铁杉状况不佳时。在有落叶物种的地区（vs. 常绿树种占主导地位，表明阿德吉德的入侵可能间接影响水刺的适应性，这取决于铁杉下降后植物的演替过程。我们的结果表明，阿德吉德（Adelgid）入侵对该河岸鸟类的短期影响在该地区很小，但这些关系可能是动态的，并取决于当地栖息地的特征和捕食者对铁杉下降的反应。