Fourageergedrag van de Grauwe Pijlstormvogel Puffinus griseus voor de Nederlandse kust

Since so far very few observations have been made of foraging Sooty Shearwaters in the Dutch coastal waters of the North Sea, in spite of its rather frequent occurrence in autumn in these waters in hard weather conditions, in this short note two different foraging strategies are described, which were observed in September and October 1987 and 1988 from a ship manned with game fishers north of the Wadden Sea isles. Since fish remains were regularly thrown overboard, the vessel was usually accompanied by flocks of gulls, Gannets and Fulmars, mixing together and fighting vigorously over pieces of fish. Sometimes these flocks were joined by a Sooty Shearwater, but these birds seemed rather more ’timid’, often waiting and hesitating at a larger distance. The ship was approached little by little and eventually the bird would join in the general fight over the fish remains. The second strategy was observed near free fishing flocks of Gannets and gulls taking advantage of Sprat driven to the surface by Mackerel. The Sooty Shearwaters flew to and fro at a moderate speed, plunge-diving now and again from low heights and at an angle of some 45°. After reappearing the bird usually stayed swimming for some time, sometimes diving again out of swimming posture. This strategy was never seen to be successful.