Trek van de Regenwulp Numenius phaeopus in Drenthe in 1980-95

Whimbrels started arriving in Drenthe in March (first dates 6 and 13 March), but mainly inApril and May with a steep peak in early May (Fig. 2). Very few birds were seen in June. Autumn migration peaked in July and August, and was less pronounced than in spring. In both spring and late summer, migration was recorded throughout the day, but especially around sunset and slightly later in late summer than in spring (Fig. 3). In spring, main flight directions were N and NE, in late summer SW (Table 1). Flock size of passing birds was greatest in April and May (mean 10.0 and 12.5 respectively, median flock size <5 birds). Most flocks (n=220) passed at heights between 15 and 50 m (42%), with 28% flying at >100 m height Flock size increased with flying height, from 8.4 birds below 50 m to 11.3 birds above 100 m.