| Summary: | Intensive seabird surveying during seven years (1992-98) in the Belgian part of the southern North Sea revealed the existence of a land-sea and a longitudinal gradient from the Schelde estuary in the east to the deeper, less turbid waters in the west. Piscivorous species preferring clear water and mid- to offshore conditions (auks, Kittiwake and Northern Gannet) are more abundant in the west. Divers, grebes and Larus-gulls are commoner in the more turbid waters near the mouth of the Schelde estuary. Depth and topography are less dominant as explanatory variables for the distribution of most of the 17 dominant species/taxa. Multivariate and correlative analysis of the abundance of these species could not reveal strong temporal or spatial coherence of seabirds in communities. Highest correlations were found among Larus-gulls scavenging at trawlers, and in the group of auks, Kittiwake and Little Gull. The auks (Razorbill, Common Guillemot) and both gull species were often seen in short-lived multi-species feeding associations over presumed fish shoals. Razorbill is the species that associated most frequently (in 28% of all observations) and it appeared to be a more ‘attractive’ target for Kittiwake (34%) and Little Gull (23%) than the Common Guillemot. Kleptoparasitic behaviour was rarely observed (2.9-6.3% of the observations in skuas). The impact of fishery activities on the distribution of scavenging seabirds (8 of the 17 dominant species) is large. Some 65-70% of all large gulls in the study area were observed in association with trawlers. The general patterns of distribution described in this paper provide the basis for new future research. Major emphasis should go to the interactions between hydrography, prey-availability (pelagic fish) and the specific geomorphologic characteristics of this study-area. Priority species for more detailed research are proposed.
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