Cory's Shearwater

Distribution, movements and phenology

The Cory's Shearwater breeds in Portugal and Spain, specifically in the Azores, Madeira, Berlengas, Peniche, Canary Islands, and the islets off the Galician coast (Equipa Atlas 2022; Reyes-González 2022). The breeding range in Portugal has remained stable for over a century (Equipa Atlas 2022). During the breeding season, from March to November, the Cory’s Shearwater is common throughout the Portuguese EEZ, showing seasonal variations in its spatial distribution. It subsequently migrates mainly to the South Atlantic, although part of the population remains in the North Atlantic or reaches the Indian Ocean (Catry et al. 2011a; Dias et al. 2011).
The Cory’s Shearwater is one of the species whose movements have been most extensively studied. Based on the individual tracking of 529 birds from Azores, Madeira, the Berlengas and the Canary Islands, fitted with GPS and PTT devices, extensive use of the Portuguese EEZ during the breeding season is noted. Activity is concentrated both in the immediate vicinity of the colonies and in more distant areas, confirming the known distribution (Meirinho et al. 2014), although in the Azores it may be biased by the greater monitoring of birds from Corvo Island.

Abundance and population trends

The global population has been estimated at between 252,000 and 253,000 pairs, with an unknown trend (BirdLife International 2025). In Portugal, there is no current information for most colonies, with a few exceptions. In the Berlengas, the population has been estimated at 550 to 800 pairs (Equipa Atlas 2022). In the Azores, recent estimates are limited to a few islets with few hundreds of pairs, namely on Vila, Vila Franca do Campo, Praia and Baixo (Atchoi 2021; (Pipa & Silva 2021; Pipa et al. 2026). On Selvagem Grande (Madeira), 38,830 pairs were estimated (Catry et al. 2025).
The assessment of environmental status indicates that the species has not achieved Good Environmental Status, either in terms of the breeding success of the Mainland or for both indicators in the Azores. On the other hand, Selvagem Grande recorded an annual growth rate of 1.45% between 2009 and 2023 (Catry et al. 2025). This population appears to be recovering from the extensive hunting in the 1970s (Zino 1985), having achieved Good Environmental Status for both indicators.

Ecology and habitat

The Cory’s Shearwater is an essentially pelagic bird that inhabits a variety of habitats, including the vicinity of colonies, seamounts, slope zones and other areas of high productivity (Paiva et al. 2010b; Ramos et al. 2013b). It feeds mainly on small epipelagic fish and cephalopods, with variations between colonies (Xavier et al. 2011; Alonso et al. 2012; Paiva et al. 2013; Alonso et al. 2018; Romero et al. 2021). It nests in natural cavities and beneath vegetation, being very rare to find exposed nests.

Threats and conservation

Their main threats are predation by mammals introduced into breeding areas and bycatch at sea. Other relevant threats include light pollution (Fontaine et al. 2011) and the potential impact of marine litter (Rodríguez et al. 2024). Conservation priorities include bycatch mitigation (Oliveira et al. 2021), the eradication of introduced predators (Hervías et al. 2013), the installation of artificial nests (Oliveira et al. 2020), the reduction of light pollution and the continuation of rescue campaigns.