Atlas of Seabirds of Portugal

Distribution, movements and phenology

The Great Cormorant has a wide distribution across all continents, with the exception of South America and Antarctica (Billerman et al. 2026). European populations breed between April and June. Some of the populations from northern and central Europe migrate and winter mainly in the south of the continent, both along the Atlantic and Mediterranean coasts (Birdlife International 2025).
In Portugal, it occurs mainly as a winter visitor from September to April, frequenting mainly coastal wetlands, but may occur across much of the Mainland (Equipa Atlas 2018). There has also been a breeding population since 2007 (Almeida 2008), located and almost entirely confined to inland Alentejo (Equipa Atlas 2022), with the main colonies situated mainly in the Guadiana River basin and, to a lesser extent, in the Sado and Tagus River basins. In the archipelagos of the Azores and Madeira, it occurs sporadically, with records mainly during autumn and winter (Meirinho et al. 2014).

Abundance and population trends

The global population is estimated at between 1,400,000 and 2,100,000 individuals, with the European population accounting for over 40%, showing an upward trend (BirdLife International 2025).
The breeding population in Mainland Portugal is estimated at 511 pairs (Equipa Atlas 2022). The wintering population in wetlands was estimated at around 1,000 individuals in 1981 (Teixeira 1984), 8,000–10,000 in the 1990s (Costa & Granadeiro 1997) and just over 15,000 individuals in 2013 (Leitão et al. 2013), with recent estimates being underestimated. Along the coast, wintering numbers show an upward trend (Alonso et al. 2022), with 1,425 individuals recorded in the winter of 2021–2022 (Fagundes & Catry 2022). Both the breeding and wintering populations have achieved Good Environmental Status for the abundance indicator.

Ecology and habitat

The Great Cormorant occurs in coastal and inland habitats, avoiding deep waters and rarely straying far from the coast (Billerman et al. 2026). In Portugal, its diet is generalist, consisting of fish such as grey mullets, Lusitanian toadfish, European eel, sand smelt and various species of annular seabream, white seabream and soles (Catry et al. 2010a; Dias et al. 2012; Granadeiro et al. 2013; Catry et al. 2017). It nests colonially in trees located on the banks of wetlands (Equipa Atlas 2022).

Threats and conservation

The main threat to the Great Cormorant appears to be associated with persecution resulting from conflicts with human activities. The perception that it has a negative impact on fish populations has led to conflicts with the fishing and aquaculture sectors, recently resulting in a proposal for a European management plan for the species, which includes measures such as culling. However, an approach based on local, proportionate measures adapted to each ecological and socio-economic context would be more advisable (Marzano et al. 2013).
In Portugal, predation on fish species of commercial value is low (Catry et al. 2010a; Granadeiro et al. 2013; Catry et al. 2017), although cases of interaction between Great Cormorants and aquaculture, recreational fishing and commercial fishing have been documented (Vieite et al. 2022). The Great Cormorant is one of the species accidentally captured as bycatch in gillnets (Oliveira et al. 2015), and is one of the most frequently encountered in the eastern Algarve (Pereira et al. 2025a).