Moult, mass and migration of Grey Plovers Pluvialis squatarola wintering in South Africa.

Data on 355 Grey Plovers Pluvialis squatarola trapped in South Africa in 1971-1997 were used to describe seasonal body mass variation and moult in relation to their very long migrations. The estimated duration of adult primary moult, 131 days, was similar to that observed in India and 30-40 days shorter than durations reported for localities in Europe. All birds in their first and second year of life oversummering in South Africa underwent a complete moult between their first boreal spring and second boreal summer. The presence of two concurrent or consecutive primary moult cycles was observed in 35% of second-year birds. It is suggested that the primary moult of first or second-year birds might be considered as an anticipated post-breeding moult rather than a postponement of the post-juvenile body moult or a delayed pre-migratory one. If this hypothesis is confirmed, the second primary moult cycle observed in oversummering first-year Grey Plovers would be a supplemental post-breedin g moult. This cycle may have no adaptive value, occurring through the absence of endogenous cues which stop the moult. Migratory mass gain was observed only in birds which had completed or suspended primary moult. Departure mass (> 310 g) was reached by some individuals as early as 15 March, but most birds departed between 15-30 April. Grey Plovers left South Africa before having moulted into a complete breeding plumage

Serra L., Whitelaw D.A., Tree A.J. & Underhill L.G., ARDEA 87 (1): 71-81.