Examining inter-regional and intra-seasonal differences in wintering waterfowl landscape associations among Pacific and Atlantic flyways

The Central Valley of California (CVC) and Mid-Atlantic (MA) in the U.S. are both critical sites for nationwide food security (California Poultry Federation 2016, Prosser et al. 2017), and many waterfowl species annually, especially during the winter, providing feeding and roosting locations for a variety of species. Mapping waterfowl distributions, using NEXRAD, may aid in the adaptive management of important waterfowl habitat and allow various government agencies to better understand the interface between wild and domestic birds and commercial agricultural practices. We used 9 years (2014–2023) of data from the US NEXRAD network to model winter waterfowl relative abundance in the CVC and MA as a function of weather, temporal period, environmental conditions, and landcover characteristics using Boosted Regression Tree modelling. We were able to quantify the variability in effect size of 28 different covariates across space and time within two geographic regions which are critical to nationwide waterfowl management and host a high density of nationally important commercial agriculture. In general, weather, geographic (distance to features), and landcover condition (wetness index) predictors had the strongest relative effect on predicting wintering waterfowl relative abundance in both regions, while effects of land cover composition were more regionally and temporally specific. Increased daily mean temperature was a major predictor of increasing relative waterfowl abundance in both regions throughout the winter. Increasing precipitation had differing effects within regions, increasing relative waterfowl abundance in the MA, while decreasing in general within the CVC. Increasing relative waterfowl abundance in the CVC is strongly tied to the flooding of the landscape and rice availability, whereas waterfowl in the MA, where water is less limiting, are generally governed by waste grain availability and emergent wetland on the landscape. Waterfowl relative abundance in the MA was generally higher nearer to the Atlantic coast and lakes, while in the CVC they were higher nearer to lakes. Our findings promote a better understanding of spatial associations of waterfowl to landscape features and may aid in conservation and biosecurity management protocols.

美国加利福尼亚中央谷（Central Valley of California, CVC）与中大西洋地区（Mid-Atlantic, MA）均为保障国家粮食安全的核心区域（加利福尼亚家禽联合会，2016；Prosser等，2017），每年都会迎来大量水鸟种群栖息，尤其在冬季，为各类物种提供了觅食与夜栖的场所。利用NEXRAD雷达绘制水鸟分布图谱，有助于对重要水鸟栖息地开展适应性管理，同时可帮助各政府部门更好地厘清野生鸟类、家养畜禽与商业化农业生产之间的交互关系。本研究使用美国NEXRAD雷达网络2014至2023年共9年的观测数据，以天气、时间周期、环境条件及土地覆被特征为自变量，采用提升回归树（Boosted Regression Tree）模型，对CVC与MA地区的冬季水鸟相对丰度开展建模分析。本研究定量分析了这两个对全国水鸟管理至关重要且聚集了大量国家级重要商业化农业生产的地理区域内，28个不同协变量的效应量随空间与时间的变化特征。总体而言，在两个研究区域中，天气、地理因子（距地物的距离）以及土地覆被状况（湿度指数）对冬季水鸟相对丰度的预测能力最强；而土地覆被组成的影响则更具区域与时间特异性。在整个冬季，日均温升高均是两个区域内水鸟相对丰度上升的关键预测因子。降水量增加对不同区域的影响存在差异：在MA地区，降水量增加会提升水鸟相对丰度，而在CVC地区则总体呈现抑制作用。CVC地区水鸟相对丰度的上升与区域内的景观淹水情况以及水稻种植资源密切相关；而MA地区水资源限制较弱，其水鸟种群丰度主要受区域内残留谷物分布与显性湿地景观的调控。MA地区的水鸟相对丰度通常在距大西洋海岸与湖泊较近的区域更高，而CVC地区的水鸟相对丰度则在邻近湖泊的区域更高。本研究结果有助于进一步厘清水鸟与景观地物之间的空间关联，可为水鸟保护与生物安全管理方案的制定提供参考。