Project Arenaria is a Citizen Science project was launched in 2009 by ISPA-Instituto Universitário, the National Natural History and Science Museum (MUHNAC) and the Portuguese Society for the Study of Birds (SPEA) to fill a gap in our knowledge of bird populations using the Portuguese coastline. The first field season aimed at assessing the population size and distribution of the shorebirds (and other waterbirds) wintering on the Portuguese mainland coast. This initial survey represents now a baseline for interpreting future population trends of wintering shorebirds in mainland Portugal. Data were also collected in the Madeira and the Azores islands.

Project Arenaria then moved forward to set an annual monitoring scheme through a sample of squares that were selected taking into account the results of the first field season. This long-term monitoring is possible thanks to the continued collaboration and support of the volunteers. The most abundant of the shorebird species monitored by this project are sanderlings Calidris alba and turnstones Arenaria interpres.

In the 2015/16 season Project Arenaria completed the second national survey of wintering coastal birds in the Portuguese non-estuarine coast, and also the first ever national survey directed at sanderlings.