Wintering waders on the Portuguese mainland non-estuarine coast: results of the 2009–2011 survey

Population estimates of wintering waders on the non-estuarine European coasts are largely based on extrapolated data from relatively small stretches of coast. In Portugal, the previous and only national estimate of waders wintering on the non-estuarine coast was based on just 7.3% of the coastline. In this study we carried out the first survey of waders wintering on almost the whole of the non-estuarine coast of Portugal, in order to improve knowledge on their abundance and distribution and to set a baseline for interpreting future population trends. The majority (96%) of the 198 5 × 5 km UTM squares, covering 1,096 km of coastline, were counted by observers walking along the shore within ±3 h of low tide during the 2009/2010 winter. 6,866 waders, of 13 species, were counted and we estimate the entire Portuguese population at 7,175. Sanderling (2,897–3,027), Ruddy Turnstone (2,191–2,289) and Kentish Plover (581–607) were the most abundant species. Highest wader numbers were found on the north and central (mainly around the Tagus estuary) coasts. The non-estuarine coast holds a significant proportion of the Portuguese winter populations of Sanderling (83.6%), Purple Sandpiper (83.3%), Ruddy Turnstone (80.1%), Whimbrel (33.5%), Kentish Plover (17.0%), Common Sandpiper (16.0%) and Eurasian Oystercatcher (15.7%). The study also highlights the international importance of the Portuguese non-estuarine coast for wintering Sanderling, Ruddy Turnstone and Kentish Plover, as the counts for these species represent ≥1% of the relevant biogeographic populations.