Pre-migratory change in mass and the migration track of a Common Sandpiper Actitis hypoleucos from Scotland

In Britain, Common Sandpipers Actitis hypoleucos mainly prepare for southward migration at coastal sites. On the Moray Firth, NE Scotland, they increased in mass at an average rate of 0.95 g (SE = 0.20) per day during late June to early August. However, there was no overall increase with date of the mean mass in the local population. A higher proportion of adults than juveniles were caught in June/early July compared to late July/August, showing that adults departed before juveniles. Common Sandpipers were fitted with geolocators in 2011 in Highland, Scotland, to track their migrations. One bird left Britain on 21 July and migrated for three days to Morocco where it staged before continuing its migration to W Africa for the non-breeding season, arriving on 29 July. The region in which it spent most of the non-breeding season (Oct–Feb) was S Senegal or The Gambia. Prior to northward migration, the bird spent a period inland, before crossing the W Sahara desert to Morocco. Its migration was then delayed, probably due to adverse weather (strong NW winds). However, after a week in Morocco, which involved some northward movement, it followed the east coast of Spain and crossed to W France before moving through England to Scotland. Although Common Sandpipers can accumulate sufficient stores for a long single non-stop flight between N Europe and W Africa, the focal bird migrated in medium-range “skips” during both its southward and northward migrations.