Extreme migration and the annual cycle:Individual strategies in New Zealand Bar-tailed Godwits
Long-distance migration places severe constraints on the annual cycles of birds, as they balance the energetic and scheduling requirements of breeding, moult, pre-migratory fuelling, and the journey itself. The most extreme migrations, traversing vast, inhospitable areas of the globe in protracted n...
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| Format: | Book |
| Language: | English |
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[S.n.]
2012
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| Online Access: | https://hdl.handle.net/11370/0e21ff4a-5a62-4547-b590-2d899bfef77b https://research.rug.nl/en/publications/0e21ff4a-5a62-4547-b590-2d899bfef77b |
| Summary: | Long-distance migration places severe constraints on the annual cycles of birds, as they balance the energetic and scheduling requirements of breeding, moult, pre-migratory fuelling, and the journey itself. The most extreme migrations, traversing vast, inhospitable areas of the globe in protracted non-stop flights, may push birds to the limits of their capabilities, and would be expected to tolerate little variation in performance. Despite this, Bar-tailed Godwits Limosa lapponia baueri , which are among the world’s greatest endurance migrants, embark on northward migration from New Zealand across a month-long period, and individuals are quite faithful to their particular schedules. Godwits are highly sexually dimorphic in plumage and body size, and there is additionally substantial individual variation within each sex in both traits. These patterns demonstrate a surprising diversity of strategies within a system that should contain little room for error. In this thesis, I sought to identify the roots and consequences of both persistent and ephemeral individual differences in migration and moult of New Zealand Bar-tailed Godwits, and to identify constraints and potential bottlenecks in their annual cycle. To do this, I combined a fine-resolution multi-year focus on individuals and an entire annual-cycle perspective, both of which have generally been impossible in studies of long-distance migratory birds. At a single non-breeding site, I closely monitored moult and migration of individual Bar-tailed Godwits for three non-breeding seasons, and linked these with events outside of New Zealand by tracking a subset of the same individuals on their complete migrations to Alaska breeding grounds and back. I supplemented this by travelling to Alaska myself and describing how godwits are distributed by size and plumage across their vast breeding range. I found that most of the variation among individual Bar-tailed Godwits was linked to where they nested in Alaska: within each sex, northerly breeders were smaller, had more ... |
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