Spring-accelerated loop migration in the Woodchat Shrike Lanius senator
摘要
The Woodchat Shrike is a long-distance migrant bird whose European populations have declined over the past decades. To inform conservation efforts, we tracked five breeding male individuals from southern France using light-level and multi-sensor loggers. We revealed a distinct anticlockwise loop migration. In autumn, birds departed from late July to mid-August, stopping for extended periods in Spain or Morocco, and again in Mauritania or Mali, before reaching their non-breeding grounds in the Sahel (eastern Mali, western Niger, northern Nigeria) by early October. The average duration of post-breeding migration was 52 days. In spring, birds departed mid-April and returned to breeding sites synchronously between April 27 and May 1. The spring route was more direct, with a significantly shorter average duration of 15 days. Stopovers were brief (median duration 20 h), and flights occurred almost exclusively at night. Only two individuals extended one nocturnal flight into daytime during spring Sahara crossings. Flight altitudes were significantly higher in spring than in autumn. These findings have important conservation implications. Woodchat Shrikes spend only three full months on breeding grounds, limiting the window for habitat management. Since they spend most of the year in sub-Saharan Africa, threats in the Sahel—such as rising temperatures, unpredictable rainfall, and land degradation—are critical. Early arrival in the Sahel may allow birds to benefit from seasonal rains there and complete their post-breeding moult.