Population densities of birds in Ørsted Dal, NE Greenland, 2009 Hans Meltofte & Lars Dinesen (Med et dansk resumé: Bestandstætheder af fugle i Ørsted Dal, Nordøstgrønland, 2009) Introduction In connection with possible molybdenum mining activities in Scoresby Land, the mining company is planning to establish an airfield together with a road, a container port and other facilities for the operations at Gurreholm in the north-western part of the Heden Ramsar Site in western Jameson Land, East Greenland (Cessford 2007, Glahder et al. 2010). To compensate for the loss of breed- ing and moulting habitat for birds in the Ramsar site, the Greenland authorities are considering the possibility to establish an alternative Ramsar site in the region. The National Environmental Re- search Institute (NERI), Aarhus University, put forward a preliminary proposal that the large val- ley of Ørsted Dal in north-eastern Jameson Land could make up such a compensation area (Glah- der et al. 2010). To study the extent to which bird populations here match populations in the lost area, NERI conducted studies in the valley in July 2008, focusing on breeding and moulting geese, and in June 2009, focusing on population densi- ties of all bird species. In parallel, similar studies were conduced in the Heden Ramsar Site (C.M. Glahder in litt.). Prior to these studies, the birds of Ørsted Dal were described in a number of papers and reports follow- ing goose and wader studies in the 1960s, 1970s and 1980s (Marris & Ogilvie 1962, Hall & Waddingham 1966, Ferns & Green 1975, Ferns & Mudge 1976, Green & Greenwood 1978, Cabot et al. 1984). In 1974 the breeding waders of a 25 km 2 study area centrally in the valley were censused in connection with an extensive wader study in the Kong Oscar Fjord region (Green & Greenwood op.cit.). This area made up one of our two study areas in the valley in June 2009, although the delineation differed some- what between the two study years. Abstract During June 2009, the bird populations in two study areas in Ørsted Dal, northern Jameson Land in NE Greenland, were censused using the "rapid assessment" method where all "territory holding" pairs and individuals are considered part of the local population. The method provided significantly higher densities of waders (Charadrii) than found in the valley at censuses in July 1974. This is interpreted as a result of all non- and failed breeders having left their territories before the July census. Yet, numbers of Ruddy Turnstones Arenaria interpres may have decreased since then, while the nesting population of Pink-footed Geese Anser brachyrhynchus has increased quite consider- ably. Also, arrival and egg-laying in Barnacle Branta leucopsis and Pink-footed geese appears to have advanced as compared to previous decades, an advancement interpreted as the result of climate amelioration. Dansk Orn. Foren. Tidsskr. 104 (2010): 59-72