Migrant waders at Aldabra, September 1967—March 1968

Abstract

Observations of palaearctic waders during the first three phases of the Royal Society Expedition to Aldabra, between 1 September 1967 and 14 March 1968 are listed and compared with those from other places in the area. Seventeen species are included in the check list, of which four are considered vagrants, and the rest more or less regular migrants. Counts made during the expedition with the intention of finding the seasonal variation in numbers of the birds have proved statistically invalid, and only a few tentative conclusions may be drawn from them. The Turnstone, Arenaria i. inter pres , may be a winter resident in fair numbers, as may the Whimbrel, Numenius p. phaeopns . Although no firm conclusion can be drawn, it is suggested that most of the other birds are passage migrants, with few staying at Aldabra for the winter. Thus the island is not an important wintering ground for any species, though it probably has some value as a resting place for the birds during their migratory flights. For the Crab Plover, Dromas ardeola , however, it may be one of the few wintering grounds where the species occurs in any numbers, and as such important. The suggestion is made that the other islands in the Indian Ocean, east of the axis of Madagascar, may function not as a destination but as a ‘safety net’ for vagrant birds or flocks.