Lebret T. (1959) De dagelijkse verplaatsingen tussen dagverblijf en nachtelijk voedselgebied bij Smienten, Anas penelope L., in enige terreinen in het lage midden van Friesland. ARDEA 47 (3-4): 199-210

1. This study deals with the daily flights of Wigeon, Anas penelope L., between daylight resting places and nocturnal feeding grounds in the province of FryslGn, the Netherlands in March 1944. 2. Two types of daylight habitat could be distinguished: A. Lakes and duck decoy ponds where no food was available. B. Inundated meadow areas where a considerable part of the Wigeon was feeding during daylight. Moreover small numbers of Wigeon were observed in partly drained inundations, where great flocks of Wigeon arrived after dusk. 3. The following distances between daylight habitat and nocturnal feeding grounds could be stated. From type A Wigeon appeared to fly over 10 km, 5 km, 7 km and 6-8 km. Wigeon from type B flighted 5-7 km. 4. The nocturnal feeding grounds were partly drained inundations. Great numbers of Wigeon were involved in flights from deep inundations to partly drained ones. Both types of inundations have positive value for Wigeon and other surface feeding ducks. Though in deep inundations, feeding possibilities are restricted this type of habitat appears most favourable as a daylight resting place. The main factor of their attractiveness appears to be that they are practically inaccessible to men. Moreover, ducks can escape birds of prey there by diving. Shallow inundations may be disturbed by men during daylight and escape by diving is very restricted. Shallow inundations however, appear to be preferable as feeding grounds. 5. The distances covered during the evening flights of the Wigeon cannot wholly be explained by the distances between daylight and nocturnal habitat. Suitable feeding grounds may have been present at much smaller distances than those actually covered. These extra distances may be explained by a strong flighting urge. Corresponding observations in many types of habitat on several species of surface feeding ducks have been made by the author showing flights+ over greater distances than could be explained as necessary results of the distances between the two habitats. 6. The biological significance of those flight patterns may be that the flighting urge at dusk induces the birds to search for new feeding grounds so that additional food stocks may be opened up. Moreover the pressure on the food stock of the daylight habitats may be diminished. A further effect may be that feeding grounds which are inaccessible for the ducks during daylight owing to disturbance by men may be used during the night, provided that there are some undisturbed daylight resting places within flighting distance.