Ardea
Official journal of the Netherlands Ornithologists' Union

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O'Hara P.D., Lank D.B. & Delgado F.S. (2002) Is the timing of moult altered by migration? Evidence from a comparison of age and residency classes of Western Sandpipers Calidris mauri in Panama. ARDEA 90 (1): 61-70
Resident species typically undergo post-nuptial moult directly following breeding, whereas long-distance migrant species usually do so after arrival at stagoing or non-breeding ('wintering') grounds. It has been suggested that moult and migration are mutually exclusive activities. If so, one will displace the other in time. We contrasted the moult timing of migrant versus non-migrant Western Sandpipers Calidris mauri, taking advantage of the fact that in Panama, most yearling birds (11-22 months of age), and some adults, were non-migratory summer residents. Yearling birds and other summer residents completed primary moult approximately 3-4 weeks earlier than adults returning from the breeding grounds. The same general pattern occurs with contour moult. Some adults of unknown migratory status also have moult patterns similar to summer residents. We interpret these patterns as indicating that earlier moult is advantageous, partially compensating residents for not migrating and breeding that year. We consider potential mechanisms that may favour an earlier moult, and discuss how moult schedules may influence Western Sandpiper migratory and life history strategies


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