SPRING MIGRATION OF TURNSTONES FROM THE BANC-DARGUIN IN MAURITANIA

Abstract

The majority of the Tumstones Arenaria interpres wintering on the Banc d'Arguin, Mauritania, probably breeds in N. Scandinavia and NW. Russia, but a sizeable proportion may be derived from Greenland and NE. Canada. Juveniles did not prepare to migrate to the breeding grounds, but in the course of spring they moved away from the study site to unknown destinations, probably nearby. The majority of adults had moulted into sum­ mer plumage by the end of April and departure was concentrated in the last week of April and the first week of May. Some immigration of Tumstones wintering further south may have occurred. Itwas calculated from the number ofrecaptured birds that approximately 1000 Tumstones retum year after year to winter at the major catching site and its immediate vicinity. During March and the beginning of April adults gained mass slowly, which may be linked to the concomitant moult into summer plumage. Calculations of the rate of body mass gain of adults recaptured in different years indicated an increase in the rate of body mass gain by the end of April. Probable departure masses vary between 130 and 140 g. From current knowledge it cannot be decided whether the Tumstones need more than one additional spring staging site to reach their breeding grounds.