Mancuso Kristen A, Fylling Megan A, Bishop Christine A, Hodges Karen E, Lancaster Michael B, Stone Katharine R
Department of Biology, University of British Columbia Okanagan, Kelowna, British Columbia, Canada.
Division of Biological Sciences, University of Montana, Missoula, MT, USA.
Mov Ecol. 2021 Mar 17;9(1):10. doi: 10.1186/s40462-021-00249-7.
For many songbirds in North America, we lack movement details about the full annual cycle, notably outside the breeding season. Understanding how populations are linked spatially between breeding and overwintering periods (migratory connectivity) is crucial to songbird conservation and management. We assessed migratory connectivity for 2 breeding populations of Gray Catbirds (Dumetella carolinensis) west of and within the Rocky Mountains by determining migration routes, stopover sites, and overwintering locations. Additionally, we compared apparent annual survivorship for both populations.
We deployed 39 archival light-level geolocators and 21 Global Positioning System (GPS) tags on catbirds in the South Okanagan Valley, British Columbia, Canada, and 32 geolocators and 52 GPS tags in the Bitterroot River Valley, Montana, USA. These devices allowed us to determine migration routes, stopover sites, overwintering locations, and migratory connectivity. Migratory connectivity was quantified using Mantel's correlation. We used mark-recapture of colour banded catbirds in both sites to estimate apparent annual survivorship.
We retrieved 6 geolocators and 19 GPS tags with usable data. Gray Catbirds from both populations passed through the Rocky Mountains eastward before heading south towards their overwintering locations in northeastern Mexico and Texas. Stopover sites during fall migration occurred primarily in Montana, Kansas, Oklahoma, and Arkansas. Overwintering locations spanned Texas and 5 states in northeastern Mexico. Individual catbirds used up to 4 distinct sites during the overwintering period. Catbirds separated by almost 500 km during the breeding season overlapped during the non-breeding season, suggesting weak migratory connectivity among western populations (Mantel's correlation = 0.013, P-value = 0.41). Catbird apparent annual survivorship estimates were higher in British Columbia (0.61 ± 0.06 females; 0.64 ± 0.05 males) than in Montana (0.34 ± 0.05 females; 0.43 ± 0.04 males), though the main driver of these differences remain unclear.
Our results provide high precision geographic details during the breeding, migration, and overwintering phases of the annual cycle for western Gray Catbirds. Notably, we found that western catbirds followed the Central Flyway as opposed to the Pacific Flyway. We document that catbirds used multiple sites over winter, contrary to the popular belief that this phase of the annual cycle is stationary for most songbirds.
对于北美许多鸣禽而言，我们缺乏其完整年度周期的活动细节，尤其是在繁殖季节之外。了解种群在繁殖期和越冬期之间的空间联系（迁徙连通性）对于鸣禽的保护和管理至关重要。我们通过确定迁徙路线、中途停歇地和越冬地点，评估了落基山脉以西和山脉内两个灰猫鹊（Dumetella carolinensis）繁殖种群的迁徙连通性。此外，我们还比较了两个种群的表观年度存活率。
我们在加拿大不列颠哥伦比亚省南奥肯那根山谷的猫鹊身上部署了39个档案光级地理定位器和21个全球定位系统（GPS）标签，在美国蒙大拿州比特鲁特河谷部署了32个地理定位器和52个GPS标签。这些设备使我们能够确定迁徙路线、中途停歇地、越冬地点和迁徙连通性。使用曼特尔相关性对迁徙连通性进行量化。我们在两个地点对彩色环志的猫鹊进行标记重捕，以估计表观年度存活率。
我们找回了6个地理定位器和19个带有可用数据的GPS标签。两个种群的灰猫鹊在向南前往墨西哥东北部和得克萨斯州的越冬地点之前，都向东穿过落基山脉。秋季迁徙期间的中途停歇地主要位于蒙大拿州、堪萨斯州、俄克拉何马州和阿肯色州。越冬地点分布在得克萨斯州和墨西哥东北部的5个州。个体猫鹊在越冬期间使用多达4个不同的地点。在繁殖季节相隔近500公里的猫鹊在非繁殖季节重叠，这表明西部种群之间的迁徙连通性较弱（曼特尔相关性 = 0.013，P值 = 0.41）。不列颠哥伦比亚省猫鹊的表观年度存活率估计值高于蒙大拿州（雌性为0.61 ± 0.06；雄性为0.64 ± 0.05）（雌性为0.34 ± 0.05；雄性为0.43 ± 0.04），尽管这些差异的主要驱动因素仍不清楚。
我们的结果提供了西部灰猫鹊年度周期中繁殖、迁徙和越冬阶段的高精度地理细节。值得注意的是，我们发现西部猫鹊遵循中央飞行路线，而不是太平洋飞行路线。我们记录到猫鹊在冬季使用多个地点，这与大多数鸣禽在年度周期的这个阶段是静止的这一普遍看法相反。
