Dunlin

Distribution, movements and phenology

The Dunlin breeds between May and July in the Arctic and in subarctic and cold temperate regions of Eurasia and North America. It subsequently migrates to temperate and tropical areas of the Northern Hemisphere (Billerman et al. 2026).
In Portugal, wintering birds originate mainly from Scandinavia and Russia, including a small proportion from the Baltic region and the United Kingdom (Delany et al. 2009). Temporarily, they are joined by birds passing through on migrations towards the north-west African coast, mostly originating from colonies in Iceland (Catry et al. 2010a; Lopes et al. 2006). The species occurs mainly in estuarine areas on the Mainland, notably in the Tagus and Sado estuaries, the Ria Formosa and the Ria de Aveiro, and is also a regular visitor to the Mondego and Guadiana estuaries. It is less common in coastal lagoons, in some reservoirs in the Alentejo interior and on the non-estuarine coast (Lecoq et al 2013; Equipa Atlas 2018). In the Azores and Madeira, it occurs only sporadically, due to their distance from the main migratory route used and the limited availability of suitable habitat on the islands.

Abundance and population trends

The global population has been estimated at between three and seven million mature individuals, with a declining trend (BirdLife International 2025). In Portugal, over 90% of the wintering population is concentrated in the Tagus and Sado estuaries, Ria Formosa and Ria de Aveiro, totalling around 40,000 birds in the early 2010s (Equipa Atlas 2018). The small proportion that uses the non-estuarine coast represents only 1% of this population (Lecoq et al 2013). Despite the increasing trend observed in Europe (Wetlands International 2025), in Portugal the species appears to be in decline in the Tagus and Sado estuaries and in the Ria Formosa, where 70 to 80% of the national population occurs (Catry et al. 2011b; Alonso et al. 2022; Belo et al. 2023; Araújo 2025), alongside a negative trend on the non-estuarine coast (Velde 2025); the species has consequently failed to achieve Good Environmental Status for the abundance indicator on the Mainland. In the Azores and Madeira, the species occurs in very small numbers (Equipa Atlas 2018). Nevertheless, the Azores population has not achieved Good Environmental Status, unlike the Madeira population.

Ecology and habitat

The Dunlin is the most common wader in the estuaries and other coastal wetlands of Mainland Portugal. It makes very little use of the non-estuarine coast, visiting the beaches adjacent to coastal lagoons and estuaries sporadically. It also actively uses salt pans and flooded agricultural fields. It feeds on small invertebrates, mainly bivalves, annelids, insect larvae, amphipods and polychaetes (Lopes et al. 1998; Lourenço 2019; Billerman et al. 2026).

Threats and conservation

The causes of the global population decline are unknown (BirdLife International 2025). At a national level, the decline in populations may stem from local factors, or from changes in their migratory and wintering areas (Catry et al. 2011b), potentially shared along the East Atlantic Flyway (Lourenço et al. 2018; Schekkerman et al. 2018; Belo et al. 2023). The degradation of some wintering areas and the potential for infrastructure development in these areas constitute significant threats, with the potential to reduce the quality of foraging areas (Catry et al. 2021). Climate change may also cause waders to shift their wintering grounds to latitudes closer to their breeding grounds, contributing to a decline in populations in more southerly regions (Rehfisch et al. 2004).

Autor

Nuno Oliveira