The Abundance and Distribution of Waterfowl Within Milford Haven After the Sea Empress Oil Spill dataset https://portal.medin.org.uk/portal/start.php?tpc=007_NRW_DS110120 This study was put in place to assess whether the oil spill was to impact the nationally important waterfowl populations found in the area of Milford Haven. Two polluted (Angle Bay and Pembroke River) and two relatively unpolluted 'control' sites (the Carew/Cresswell and Cleddau Rivers) were monitored intensively over the three winters after the oil spill. The four sites have been monitored following standard Wetland Bird Survey (WeBS) methodology to assess the numbers of waterfowl present, and following standard British Trust for Ornithology all-day (across the tidal cycle) count methodology to assess the feeding areas most used. The data was captured to assess the impact of the Sea Empress oil spill on waterfowl populations in the Milford Haven area. Counts during winter took place between November and March as the estuary is most important for birds during the winter period. The migration and early autumn periods have been excluded because numbers of birds can fluctuate widely from year to year, for reasons not associated with the estuary. Each site was counted twice a month with one count on a spring tide and one on a neap tide where possible. In the first year, only one count was carried out at each site in November. Historical data was used from 1982-1999. 20001031