Extreme changes to key waterfowl habitats in the Klamath Basin (KB) on the Oregon–California border and the Sacramento Valley (SV) in California, USA, have occurred since 1980. The spatial distribution of Pacific greater white‐fronted geese (Anser albifrons sponsa; geese) has likewise changed among these areas and population size has grown from 79,000 to >600,000 geese during the same period. To assess the effects of landscape changes and spatial‐temporal distribution of geese, we collected Pacific greater white‐fronted geese during winters of 2009–2010 and 2010–2011 in the KB and SV and compared their body condition to geese collected during 1979–1980 and 1980–1981. We modeled body and lipid mass to assess body condition for each sex independently and examined the influence of collection day, year, and region. Body condition of geese varied throughout the winter and within years in a nonlinear fashion. We detected an increase in body condition in both sexes during December and January in the SV, which corresponds with improved habitat conditions and increases seen in other species in the region. Body condition upon arrival in fall migration varied by year for females and by year and region for males. Males and females arrived in poorer body condition during 2010–2011 than all other study years and males in the KB during 2010–2011 had extremely low lipid mass, reflecting poor regional habitat conditions induced by drought. Body condition of females varied over spring, by year, and by region and regional effects were evident for males. Body condition was significantly higher for geese in the SV than in the KB during spring. Our results suggest that Pacific greater white‐fronted geese have adapted to a changing landscape and have adjusted historical spatial use patterns to take advantage of more favorable conditions in the SV between 1979 and 2010. © 2021 The Wildlife Society.

中文翻译：

---

越冬太平洋大白额雁的身体状况

自1980年以来，俄勒冈-加利福尼亚边界的克拉马斯盆地（KB）和美国加利福尼亚的萨克拉曼多谷（SV）的主要水禽栖息地发生了极端变化。太平洋大白额雁（Anser albifrons sponsa）的空间分布; 鹅在这些地区之间也发生了变化，同一时期的人口规模从79,000只增加到了600,000只以上。为了评估鹅的景观变化和时空分布的影响，我们在KB和SV中收集了2009-2010年和2010-2011年冬季太平洋大白额鹅，并将它们的身体状况与1979-1980年期间收集的鹅进行了比较和1980–1981年。我们对身体和脂质质量进行建模，以独立评估每种性别的身体状况，并检查采集日期，年份和地区的影响。鹅的身体状况在整个冬季和数年内以非线性方式变化。我们在SV的12月和1月发现两性的身体状况都有所增加，这与栖息地状况的改善和该地区其他物种的生活状况增加是相对应的。秋季迁徙时的身体状况对于女性而言有所不同，对于男性而言，则根据年份和地区而有所不同。与其他所有研究年份相比，2010-2011年期间男性和女性的身体状况较差，2010-2011年期间KB中的男性脂质含量极低，这反映了干旱引起的区域生境条件差。女性的身体状况在春季，一年中有所不同，并且按地区和地区的影响对于男性来说是明显的。在春季，SV中的鹅的身体状况显着高于KB中的鹅。我们的研究结果表明，太平洋大白额雁已经适应了不断变化的景观，并调整了历史空间利用模式，以利用1979年至2010年间南美洲小陆虎的更有利条件。©2021野生动物协会。