The effects of intertidal oyster culture on the spatial distribution of waterbirds

Intertidal oyster cultivation is a widespread activity and has the potential to cause negative impacts to waterbirds. The aim of this study was to determine whether waterbird species show positive, neutral, or negative patterns of association with the presence of oyster trestles. We carried out an extensive study across six sites, and an intensive study at one site, in southern Ireland, to examine waterbird distribution patterns in relation to the presence of intertidal oyster cultivation. Grey Plover Pluvialis squatarola, Red Knot Calidris canutus, Dunlin C. alpina and Bar-tailed Godwit Limosa lapponica, and a further six species with more limited data, showed strong negative patterns of association with oyster trestles. Eurasian Oystercatcher Haematopus ostralegus, Redshank Tringa totanus, Ruddy Turnstone Arenaria interpres and European Herring Gull Larus argentatus showed neutral/positive patterns of association. Five other species showed negative patterns of association at some sites, and neutral/positive patterns at other sites. A few waterbird species may benefit from the presence of oyster trestles, but many intertidal waterbird species in typical north-western European coastal sites show a negative association with the presence of oyster trestles, at least at some sites, highlighting the importance of carrying out site-specific assessments of the impact of intertidal oyster culture on waterbird populations.