Atlas of Seabirds of Portugal

Distribution, movements and phenology

The European Shag breeds between February and August, and is found along the European Atlantic coast, in north-west Africa, the Mediterranean and the Black Sea (Billerman et al. 2026). It is a predominantly sedentary species, concentrating its distribution around colonies throughout the year (Velando et al. 2005; Nascimento et al. 2023b). However, some birds undertake short-distance migrations during winter and juveniles exhibit some dispersive movements.

In Portugal, it breeds exclusively on the Mainland, in the Berlengas archipelago and on the rocky coast between Cape Carvoeiro and Albufeira (del Moral & Oliveira 2019). Individual tracking confirmed the localised distribution around breeding colonies. Juveniles undertook more extensive dispersal movements, with one reaching the coastal area between Matosinhos and Caminha during its first winter. Previous records in this part of the country were attributed to individuals originating from Galician colonies (Catry et al. 2010a). There are no known records of the European Shag in the Azores (Meirinho et al. 2014; Birding Azores 2022) and although the species is recognised as occasional in the Madeira archipelago (Correia-Fagundes et al. 2021), only one record of an individual was confirmed in the 1990s (Zino et al. 1995a).

Abundance and population trends

The global population has been estimated at 230,000 to 240,000 individuals (Wetlands International 2025), with a declining trend (BirdLife International 2025). In Portugal, it is a scarce species. In 2017, 101 breeding pairs were recorded along the Portuguese Mainland coast (del Moral & Oliveira 2019). The largest colony, comprising 62 pairs, was located in the Berlengas archipelago, followed by the Arrábida/Cape Espichel area, where 20 pairs were recorded. No substantial change in the species’ distribution has been recorded since the last census, carried out in 2002 (Equipa Atlas 2022). However, a considerable decline in the population size of the Berlengas archipelago and the south-west coast should be noted. The assessment of environmental status is consistent with this trend, with the population failing to achieve Good Environmental Status for either indicator, abundance or productivity.

Ecology and habitat

It is a coastal species that inhabits rocky habitats and does not venture out into the open sea. It feeds on a wide variety of pelagic, demersal and benthic fish, with the sand eel being the main species consumed during the breeding season in Portugal (Nascimento et al. 2021). Outside this period, the European Shag has an even more diverse diet, being particularly rich in gadids and sparids. It nests singly or in small colonies on coastal cliffs, islands and islets. The nest is built on ledges, in crevices and caves, which are generally sheltered.

Threats and conservation

Although its diet is relatively flexible, the species depends on certain prey, and a shortage of these resources could jeopardise its survival (BirdLife International 2025). Climate change contributes to a decline in prey numbers and an increase in the frequency of extreme weather events. Oil pollution causes direct mortality and indirect ecological impacts on the habitat (Velando et al. 2005). The species is also vulnerable to competition with commercial fisheries as they exploit shared prey (Nascimento et al. 2021; Nascimento et al. 2023b). This trophic overlap is particularly relevant during winter, when prey availability may be lower. The species is also vulnerable to bycatch in gillnets and longlines (Oliveira et al. 2021).