|Feeding behaviour of Oystercatchers (Haematopus ostralegus) during a period of tidal manipulations|
Meire, P. (1996). Feeding behaviour of Oystercatchers (Haematopus ostralegus) during a period of tidal manipulations. Ardea 84A(SI): 509-524
In: Ardea. Nederlandse Ornithologische Unie: Arnhem; Leiden. ISSN 0373-2266, more
Oystercatcher; Haematopus ostralegus; time stress; optimal foraging;maximum food intake rate; consumption deficit; compensation
Due to the construction of a storm surge barrier in the mouth of the Oosterschelde, the tidal amplitude in the estuary can be manipulated. In this paper I describe the effects of a closure during the autumn of 1986 on the numbers, distribution and foraging behaviour of Oystercatchers. During the closure, which lasted for six consecutive tides, the water level remained high and only the upper part of the intertidal area was exposed. Oystercatchers spent most of their time feeding in this zone, where they normally spent only a very short time during their movement down to the preferred feeding areas below mid-tidal level. When feeding conditions further deteriorated during a severe gale, birds stopped feeding altogether. When the tidal regime was restored, birds distributed themselves over the feeding areas as before. It was calculated from measurements of food intake that, during the closure of the barrier, a bird, on average, obtained only two thirds of the food that it would have taken under normal conditions. If Oystercatchers are able to increase their intake rates above normally observed levels, they would have been expected to do so as soon as they were able to feed again on their preferred feeding areas. However no change in intake rates took place, indicating that Oystercatchers generally feed at their maximum rates. This contrasts with some experimental results. Total numbers of birds in the study area during this period of closure were not affected, although the consumption deficit could have influenced their condition.