Abstract

Migratory species are acutely vulnerable to habitat loss, especially for migratory birds that rely on multiple stopover sites during migration. Typically, migratory birds show less exploratory behavior as they age, i.e., their migration routes typically become more fixed, which leads to higher vulnerability to habitat change. Indeed, due to habitat loss and land use changes in the East Asian-Australasian Flyway, most waterbird populations have rapidly declined, but there are some notable exceptions. We hypothesized that species with stable or growing population may be those able to maintain migration behavioral flexibility into adulthood, enabling them to cope better with environmental change. To test this hypothesis, we used satellite tracking technology to monitor the movement behaviors of Pied Avocets Recurvirostra avosetta, an increasing species highly adapted to artificial wetlands in the East Asian-Australasian Flyway. We compared the migration behaviors of 48 adult and 20 juvenile Pied Avocets in eastern China. In the first two years of life, Pied Avocets performed relatively limited movements. In contrast, some adults migrated to much more southerly wintering grounds or more northerly breeding sites, and occasionally pioneered entirely new flight paths. Additionally, adult birds showed greater variability in their movements during the non-migration period, indicating that older individuals retain behavioral flexibility, likely in response to environmental changes. This suggests that flexible migration strategies in adult animals may enhance resilience to habitat alterations and might help predict which species will be especially vulnerable to environmental change.