Ardea
Official journal of the Netherlands Ornithologists' Union

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Summers R.W., Underhill L.G. & Prys-Jones R.P. (1995) Why do young waders in southern Africa delay their first return migration to the breeding grounds? ARDEA 83 (2): 351-357
The numbers of northern breeding waders over-summering at estuaries in Britain and at Langebaan Lagoon, South Africa, were expressed as a percentage of the previous winter's population to give a measure of delayed return migration of young birds. A higher percentage of waders over-summered in South Africa compared with Britain. Also, a higher percentage of large waders over-summered in South Africa compared with small waders. The percentage of over-summering Curlew Sandpipers was related to the percentage of first-year birds in winter, suggesting that all may over-summer. Mass, moult and gonad size of these young birds confirmed that they do not migrate north with the adults. We suggest that delayed migration is related to the risk of migration, but modified by longevity.


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