Piersma T., Klaassen M., Bruggemann, J.H. Blomert A.M., Gueye A., Ntiamoa B.Y. & Van Brederode N.E. (1990) Seasonal timing of the spring departure of waders from the Banc d'Arguin Mauritania. ARDEA 78 (1-2): 123-134

The northward departure of 13 wader species was studied in the Baie d'Aouatif, Banc d'Arguin, Mauritania, in the springs of 1985, 1986 and 1988. Waders left the area in the late afternoon. Wind speed and direction were registered near ground level (all years) and at altitudes up to 5 km (in 1988). A total of 31 000 waders were observed heading northwards, with those species wintering locally in largest numbers being most common. The majority of wader species showed fairly short periods of departure and unimodal departure peaks. Redshank and Dunlin departed over extended periods. Average departure dates of species correlated positively with the estimated midpoints of ranges in breeding latitude (ca. 2 d per .degree. latitude). Since winds at ground level did not correlate with winds at higher altitudes, and since it is likely that the departing waders traveled at great heights, it was not surprising that there is no correlation between the average afternoon tail wind vector at ground level and the daily departure intensity. We suggest that the timing of departure from the Banc d' Arguin is largely under internal, instead of under direct environmental, control.