Tracking data demonstrate plasticity in migration behaviour of the East Asian Pied Avocet Recurvirostra avosetta

Avian populations showing a diversity of migration patterns are more likely resilient to environmental changes and less likely to decline in response to factors such as climate change and habitat loss, making knowledge of how migration behaviour varies spatially and temporally within and between individuals crucial for their successful conservation. We tracked 31 migratory episodes in six East Asian Pied Avocets, identifying migration behaviour and annual schedules over 5 consecutive years. The Pied Avocets spent means of 195 days on summering areas, 108 days on wintering areas, 24 days on autumn (9 November–3 December), and 27 days on spring (23 March–19 April), with considerable individual variation. Individuals also exhibited significant variability in migration distance (mean of 977 ± 347 km and 1,261 ± 507 km in autumn and spring, respectively), migration speed, stopover duration and site fidelity. Some birds showed consistent between-year migration patterns and site fidelity, others did not. Four individuals exhibited highly peripatetic summer schedules, implying sampling between inland arid and coastal wetlands for potential nesting sites. Our results supplement recent studies by providing new valuable insights into individual behavioural plasticity on migration with long-term tracking data and new knowledge about previously unknown summering areas in the Northern Yellow Sea, NE China, Inner Mongolia, and NW Hebei, also confirming the importance of known wintering areas in the Southern Yellow Sea, the Yangtze River and the Huai River floodplain. We urge prudence in concluding too much from our limited sample size and further tracking of more individuals.