Fuelling and moult in Red Knots before northward departure:A visual evaluation of differences between ages, sexes and subspecies

• Published in: Emu - Austral Ornithology
• Main Authors: Verhoeven, Mo A., van Eerbeek, Joop, Hassell, Chris J., Piersma, Theunis
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Roebuck; Calidris canutus; Red Knot
• Online Access: https://hdl.handle.net/11370/23cdc871-25c6-4e66-957c-8e4970d33dde; https://research.rug.nl/en/publications/23cdc871-25c6-4e66-957c-8e4970d33dde; https://doi.org/10.1071/MU15035; https://pure.rug.nl/ws/files/134743322/Fuelling_and_moult_in_Red_Knots_before_northward_departure_A_visual.pdf

The departure of migratory birds from their non-breeding grounds is thought to be driven by the phenology of their breeding destination. In north-west Australia, two plumage morphs of Red Knot ( Calidris canutus ) prepare for a 5500-km journey to Yellow Sea staging areas. These morphs are recognised as the subspecies C. c. piersmai and C. c. rogers i, which breed at different latitudes and have different seasonalities. From February to May 2011, we observed the migratory preparation of individually marked birds of known age, sex and type. This enabled a comparison of fuelling rates and pre-alternate moult among these classes. First-year birds did not prepare for migration. Second-year birds accumulated smaller fuel stores and reached lower plumage scores than adults. Adults of both types reached their highest abdominal profile scores by the end of April when they were last observed in Roebuck Bay. This lack of difference between types in the timing of fuelling and departure is surprising. Based on the differences in staging and breeding phenology, C. c. rogersi is expected to leave north-west Australia 2–4 weeks before C. c. piersmai . Assuming that types and subspecies are equivalent, our findings in combination with other research on Red Knots in the East Asian–Australasian Flyway suggest that it takes more than breeding origin alone to explain annual cycles in migratory birds. Concurrent migratory schedules imply that, during northward staging in the Yellow Sea, there is strong variation in fuelling rates between and within subspecies depending on non-breeding origin. The ongoing loss of staging habitat may therefore have differential effects on Red Knots in the East Asian–Australasian Flyway.