Atlas of Seabirds of Portugal

Distribution, movements and phenology

The Little Tern breeds in Eurasia, Africa and Australia (Billerman et al. 2026). In Europe, it occurs as a subspecies, with the breeding season taking place between April and July. In Mainland Portugal, the largest colonies are found on the sandy islands of the Ria Formosa, with an increasingly rare occurrence in the salt pans of this area. In smaller numbers, it nests in other wetlands and coastal areas, such as the Ria de Aveiro and the estuaries of the Mondego, Tagus and Sado rivers, or inland, in the Caia and Alqueva reservoirs (Equipa Atlas 2022). During the post-breeding period, between August and September, breeding birds are also found in other European countries, en route to the west coast of Africa (Equipa Atlas 2018), a destination also common to the national population (Catry et al. 2010a). Data from 20 birds fitted with GPS between 2021 and 2025 on Barreta Island (Ria Formosa) indicate that they are found primarily in the lagoon, salt pans and sea adjacent to the breeding colonies, and may undertake offshore journeys of up to 20 km (Cerveira et al. 2025). It is worth noting that one individual, after losing its clutch, crossed the Gulf of Cádiz to Spain. In the archipelagos of Madeira and the Azores, the species is rare.

Abundance and population trends

The global population has been estimated at between 190,000 and 410,000 individuals, of which 36,000 to 53,000 pairs breed in Europe (BirdLife International 2025). The breeding population in Portugal has shown marked fluctuations over the years, with the most recent estimate pointing to 558 to 943 pairs (Equipa Atlas 2022). The Ria Formosa hosts Portugal’s main breeding concentration, with an estimated population of 303 to 522 pairs between 2020 and 2025, mostly on sandy beaches near the tidal inlets. Despite localised declines in some colonies, the significant increase in the Ria Formosa population appears to account for the positive trend at national level. This pattern was corroborated by the assessment presented in this work, which indicates that the species has achieved Good Environmental Status for the abundance indicator. Regarding the migratory population or the situation in the Azores and Madeira, there is no information on abundance that would allow an assessment of its environmental status.

Ecology and habitat

The Little Tern nests in coastal wetlands, sandy beaches, sandbanks and salt pans with little disturbance (Equipa Atlas 2008; Catry et al. 2010a) and reduced vegetation cover (Lopes et al. 2015). It uses a small depression in the sand or soil as a nest. The species forages around its breeding areas, exploiting inland waters, salt pans, aquaculture sites and also shallow coastal waters (Paiva et al. 2008). The main prey of the Little Tern are small fish, particularly sand smelt and gobies in Portuguese waters (Catry et al. 2006; Ramos et al. 2013a). To a lesser extent, it also consumes white seabreams, garfish, sardines, crustaceans and insects (Correia et al. 2016).

Threats and conservation

In Portugal, the main threats to the Little Tern are human disturbance in breeding areas and the abandonment of salt pans, with the consequent increase in vegetation cover around the ponds (Medeiros et al. 2007; Equipa Atlas 2022). Predation by mammals and birds, particularly by dogs, cats, Eurasian Thick-knee Burhinus oedicnemus or Carrion Crows Corvus corone, is also a significant threat (Catry et al. 2004). Human disturbance in breeding areas can be controlled and reduced through fencing and temporary closure of the main breeding colonies (Medeiros et al. 2007). Vegetation management, predator control and the construction of artificial islands in these same areas increase the productivity and stability of the colonies. Such measures are being implemented in the Ria Formosa.